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remarkable-linux/kernel/bpf/verifier.c
Daniel Borkmann 4cabc5b186 bpf: fix mixed signed/unsigned derived min/max value bounds 
Edward reported that there's an issue in min/max value bounds
tracking when signed and unsigned compares both provide hints
on limits when having unknown variables. E.g. a program such
as the following should have been rejected:

   0: (7a) *(u64 *)(r10 -8) = 0
   1: (bf) r2 = r10
   2: (07) r2 += -8
   3: (18) r1 = 0xffff8a94cda93400
   5: (85) call bpf_map_lookup_elem#1
   6: (15) if r0 == 0x0 goto pc+7
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R10=fp
   7: (7a) *(u64 *)(r10 -16) = -8
   8: (79) r1 = *(u64 *)(r10 -16)
   9: (b7) r2 = -1
  10: (2d) if r1 > r2 goto pc+3
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R1=inv,min_value=0
  R2=imm-1,max_value=18446744073709551615,min_align=1 R10=fp
  11: (65) if r1 s> 0x1 goto pc+2
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R1=inv,min_value=0,max_value=1
  R2=imm-1,max_value=18446744073709551615,min_align=1 R10=fp
  12: (0f) r0 += r1
  13: (72) *(u8 *)(r0 +0) = 0
  R0=map_value_adj(ks=8,vs=8,id=0),min_value=0,max_value=1 R1=inv,min_value=0,max_value=1
  R2=imm-1,max_value=18446744073709551615,min_align=1 R10=fp
  14: (b7) r0 = 0
  15: (95) exit

What happens is that in the first part ...

   8: (79) r1 = *(u64 *)(r10 -16)
   9: (b7) r2 = -1
  10: (2d) if r1 > r2 goto pc+3

... r1 carries an unsigned value, and is compared as unsigned
against a register carrying an immediate. Verifier deduces in
reg_set_min_max() that since the compare is unsigned and operation
is greater than (>), that in the fall-through/false case, r1's
minimum bound must be 0 and maximum bound must be r2. Latter is
larger than the bound and thus max value is reset back to being
'invalid' aka BPF_REGISTER_MAX_RANGE. Thus, r1 state is now
'R1=inv,min_value=0'. The subsequent test ...

  11: (65) if r1 s> 0x1 goto pc+2

... is a signed compare of r1 with immediate value 1. Here,
verifier deduces in reg_set_min_max() that since the compare
is signed this time and operation is greater than (>), that
in the fall-through/false case, we can deduce that r1's maximum
bound must be 1, meaning with prior test, we result in r1 having
the following state: R1=inv,min_value=0,max_value=1. Given that
the actual value this holds is -8, the bounds are wrongly deduced.
When this is being added to r0 which holds the map_value(_adj)
type, then subsequent store access in above case will go through
check_mem_access() which invokes check_map_access_adj(), that
will then probe whether the map memory is in bounds based
on the min_value and max_value as well as access size since
the actual unknown value is min_value <= x <= max_value; commit
fce366a9dd ("bpf, verifier: fix alu ops against map_value{,
_adj} register types") provides some more explanation on the
semantics.

It's worth to note in this context that in the current code,
min_value and max_value tracking are used for two things, i)
dynamic map value access via check_map_access_adj() and since
commit 06c1c04972 ("bpf: allow helpers access to variable memory")
ii) also enforced at check_helper_mem_access() when passing a
memory address (pointer to packet, map value, stack) and length
pair to a helper and the length in this case is an unknown value
defining an access range through min_value/max_value in that
case. The min_value/max_value tracking is /not/ used in the
direct packet access case to track ranges. However, the issue
also affects case ii), for example, the following crafted program
based on the same principle must be rejected as well:

   0: (b7) r2 = 0
   1: (bf) r3 = r10
   2: (07) r3 += -512
   3: (7a) *(u64 *)(r10 -16) = -8
   4: (79) r4 = *(u64 *)(r10 -16)
   5: (b7) r6 = -1
   6: (2d) if r4 > r6 goto pc+5
  R1=ctx R2=imm0,min_value=0,max_value=0,min_align=2147483648 R3=fp-512
  R4=inv,min_value=0 R6=imm-1,max_value=18446744073709551615,min_align=1 R10=fp
   7: (65) if r4 s> 0x1 goto pc+4
  R1=ctx R2=imm0,min_value=0,max_value=0,min_align=2147483648 R3=fp-512
  R4=inv,min_value=0,max_value=1 R6=imm-1,max_value=18446744073709551615,min_align=1
  R10=fp
   8: (07) r4 += 1
   9: (b7) r5 = 0
  10: (6a) *(u16 *)(r10 -512) = 0
  11: (85) call bpf_skb_load_bytes#26
  12: (b7) r0 = 0
  13: (95) exit

Meaning, while we initialize the max_value stack slot that the
verifier thinks we access in the [1,2] range, in reality we
pass -7 as length which is interpreted as u32 in the helper.
Thus, this issue is relevant also for the case of helper ranges.
Resetting both bounds in check_reg_overflow() in case only one
of them exceeds limits is also not enough as similar test can be
created that uses values which are within range, thus also here
learned min value in r1 is incorrect when mixed with later signed
test to create a range:

   0: (7a) *(u64 *)(r10 -8) = 0
   1: (bf) r2 = r10
   2: (07) r2 += -8
   3: (18) r1 = 0xffff880ad081fa00
   5: (85) call bpf_map_lookup_elem#1
   6: (15) if r0 == 0x0 goto pc+7
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R10=fp
   7: (7a) *(u64 *)(r10 -16) = -8
   8: (79) r1 = *(u64 *)(r10 -16)
   9: (b7) r2 = 2
  10: (3d) if r2 >= r1 goto pc+3
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R1=inv,min_value=3
  R2=imm2,min_value=2,max_value=2,min_align=2 R10=fp
  11: (65) if r1 s> 0x4 goto pc+2
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0
  R1=inv,min_value=3,max_value=4 R2=imm2,min_value=2,max_value=2,min_align=2 R10=fp
  12: (0f) r0 += r1
  13: (72) *(u8 *)(r0 +0) = 0
  R0=map_value_adj(ks=8,vs=8,id=0),min_value=3,max_value=4
  R1=inv,min_value=3,max_value=4 R2=imm2,min_value=2,max_value=2,min_align=2 R10=fp
  14: (b7) r0 = 0
  15: (95) exit

This leaves us with two options for fixing this: i) to invalidate
all prior learned information once we switch signed context, ii)
to track min/max signed and unsigned boundaries separately as
done in [0]. (Given latter introduces major changes throughout
the whole verifier, it's rather net-next material, thus this
patch follows option i), meaning we can derive bounds either
from only signed tests or only unsigned tests.) There is still the
case of adjust_reg_min_max_vals(), where we adjust bounds on ALU
operations, meaning programs like the following where boundaries
on the reg get mixed in context later on when bounds are merged
on the dst reg must get rejected, too:

   0: (7a) *(u64 *)(r10 -8) = 0
   1: (bf) r2 = r10
   2: (07) r2 += -8
   3: (18) r1 = 0xffff89b2bf87ce00
   5: (85) call bpf_map_lookup_elem#1
   6: (15) if r0 == 0x0 goto pc+6
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R10=fp
   7: (7a) *(u64 *)(r10 -16) = -8
   8: (79) r1 = *(u64 *)(r10 -16)
   9: (b7) r2 = 2
  10: (3d) if r2 >= r1 goto pc+2
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R1=inv,min_value=3
  R2=imm2,min_value=2,max_value=2,min_align=2 R10=fp
  11: (b7) r7 = 1
  12: (65) if r7 s> 0x0 goto pc+2
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R1=inv,min_value=3
  R2=imm2,min_value=2,max_value=2,min_align=2 R7=imm1,max_value=0 R10=fp
  13: (b7) r0 = 0
  14: (95) exit

  from 12 to 15: R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0
  R1=inv,min_value=3 R2=imm2,min_value=2,max_value=2,min_align=2 R7=imm1,min_value=1 R10=fp
  15: (0f) r7 += r1
  16: (65) if r7 s> 0x4 goto pc+2
  R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R1=inv,min_value=3
  R2=imm2,min_value=2,max_value=2,min_align=2 R7=inv,min_value=4,max_value=4 R10=fp
  17: (0f) r0 += r7
  18: (72) *(u8 *)(r0 +0) = 0
  R0=map_value_adj(ks=8,vs=8,id=0),min_value=4,max_value=4 R1=inv,min_value=3
  R2=imm2,min_value=2,max_value=2,min_align=2 R7=inv,min_value=4,max_value=4 R10=fp
  19: (b7) r0 = 0
  20: (95) exit

Meaning, in adjust_reg_min_max_vals() we must also reset range
values on the dst when src/dst registers have mixed signed/
unsigned derived min/max value bounds with one unbounded value
as otherwise they can be added together deducing false boundaries.
Once both boundaries are established from either ALU ops or
compare operations w/o mixing signed/unsigned insns, then they
can safely be added to other regs also having both boundaries
established. Adding regs with one unbounded side to a map value
where the bounded side has been learned w/o mixing ops is
possible, but the resulting map value won't recover from that,
meaning such op is considered invalid on the time of actual
access. Invalid bounds are set on the dst reg in case i) src reg,
or ii) in case dst reg already had them. The only way to recover
would be to perform i) ALU ops but only 'add' is allowed on map
value types or ii) comparisons, but these are disallowed on
pointers in case they span a range. This is fine as only BPF_JEQ
and BPF_JNE may be performed on PTR_TO_MAP_VALUE_OR_NULL registers
which potentially turn them into PTR_TO_MAP_VALUE type depending
on the branch, so only here min/max value cannot be invalidated
for them.

In terms of state pruning, value_from_signed is considered
as well in states_equal() when dealing with adjusted map values.
With regards to breaking existing programs, there is a small
risk, but use-cases are rather quite narrow where this could
occur and mixing compares probably unlikely.

Joint work with Josef and Edward.

  [0] https://lists.iovisor.org/pipermail/iovisor-dev/2017-June/000822.html

Fixes: 484611357c ("bpf: allow access into map value arrays")
Reported-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-07-20 15:20:27 -07:00

3920 lines
112 KiB
C
Raw Blame History

/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
* Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/bpf_verifier.h>
#include <linux/filter.h>
#include <net/netlink.h>
#include <linux/file.h>
#include <linux/vmalloc.h>
#include <linux/stringify.h>
/* bpf_check() is a static code analyzer that walks eBPF program
* instruction by instruction and updates register/stack state.
* All paths of conditional branches are analyzed until 'bpf_exit' insn.
*
* The first pass is depth-first-search to check that the program is a DAG.
* It rejects the following programs:
* - larger than BPF_MAXINSNS insns
* - if loop is present (detected via back-edge)
* - unreachable insns exist (shouldn't be a forest. program = one function)
* - out of bounds or malformed jumps
* The second pass is all possible path descent from the 1st insn.
* Since it's analyzing all pathes through the program, the length of the
* analysis is limited to 64k insn, which may be hit even if total number of
* insn is less then 4K, but there are too many branches that change stack/regs.
* Number of 'branches to be analyzed' is limited to 1k
*
* On entry to each instruction, each register has a type, and the instruction
* changes the types of the registers depending on instruction semantics.
* If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
* copied to R1.
*
* All registers are 64-bit.
* R0 - return register
* R1-R5 argument passing registers
* R6-R9 callee saved registers
* R10 - frame pointer read-only
*
* At the start of BPF program the register R1 contains a pointer to bpf_context
* and has type PTR_TO_CTX.
*
* Verifier tracks arithmetic operations on pointers in case:
* BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
* BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
* 1st insn copies R10 (which has FRAME_PTR) type into R1
* and 2nd arithmetic instruction is pattern matched to recognize
* that it wants to construct a pointer to some element within stack.
* So after 2nd insn, the register R1 has type PTR_TO_STACK
* (and -20 constant is saved for further stack bounds checking).
* Meaning that this reg is a pointer to stack plus known immediate constant.
*
* Most of the time the registers have UNKNOWN_VALUE type, which
* means the register has some value, but it's not a valid pointer.
* (like pointer plus pointer becomes UNKNOWN_VALUE type)
*
* When verifier sees load or store instructions the type of base register
* can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, FRAME_PTR. These are three pointer
* types recognized by check_mem_access() function.
*
* PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
* and the range of [ptr, ptr + map's value_size) is accessible.
*
* registers used to pass values to function calls are checked against
* function argument constraints.
*
* ARG_PTR_TO_MAP_KEY is one of such argument constraints.
* It means that the register type passed to this function must be
* PTR_TO_STACK and it will be used inside the function as
* 'pointer to map element key'
*
* For example the argument constraints for bpf_map_lookup_elem():
* .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
* .arg1_type = ARG_CONST_MAP_PTR,
* .arg2_type = ARG_PTR_TO_MAP_KEY,
*
* ret_type says that this function returns 'pointer to map elem value or null'
* function expects 1st argument to be a const pointer to 'struct bpf_map' and
* 2nd argument should be a pointer to stack, which will be used inside
* the helper function as a pointer to map element key.
*
* On the kernel side the helper function looks like:
* u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
* {
* struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
* void *key = (void *) (unsigned long) r2;
* void *value;
*
* here kernel can access 'key' and 'map' pointers safely, knowing that
* [key, key + map->key_size) bytes are valid and were initialized on
* the stack of eBPF program.
* }
*
* Corresponding eBPF program may look like:
* BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
* BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
* BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
* BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
* here verifier looks at prototype of map_lookup_elem() and sees:
* .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
* Now verifier knows that this map has key of R1->map_ptr->key_size bytes
*
* Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
* Now verifier checks that [R2, R2 + map's key_size) are within stack limits
* and were initialized prior to this call.
* If it's ok, then verifier allows this BPF_CALL insn and looks at
* .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
* R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
* returns ether pointer to map value or NULL.
*
* When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
* insn, the register holding that pointer in the true branch changes state to
* PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
* branch. See check_cond_jmp_op().
*
* After the call R0 is set to return type of the function and registers R1-R5
* are set to NOT_INIT to indicate that they are no longer readable.
*/
/* verifier_state + insn_idx are pushed to stack when branch is encountered */
struct bpf_verifier_stack_elem {
/* verifer state is 'st'
* before processing instruction 'insn_idx'
* and after processing instruction 'prev_insn_idx'
*/
struct bpf_verifier_state st;
int insn_idx;
int prev_insn_idx;
struct bpf_verifier_stack_elem *next;
};
#define BPF_COMPLEXITY_LIMIT_INSNS 98304
#define BPF_COMPLEXITY_LIMIT_STACK 1024
#define BPF_MAP_PTR_POISON ((void *)0xeB9F + POISON_POINTER_DELTA)
struct bpf_call_arg_meta {
struct bpf_map *map_ptr;
bool raw_mode;
bool pkt_access;
int regno;
int access_size;
};
/* verbose verifier prints what it's seeing
* bpf_check() is called under lock, so no race to access these global vars
*/
static u32 log_level, log_size, log_len;
static char *log_buf;
static DEFINE_MUTEX(bpf_verifier_lock);
/* log_level controls verbosity level of eBPF verifier.
* verbose() is used to dump the verification trace to the log, so the user
* can figure out what's wrong with the program
*/
static __printf(1, 2) void verbose(const char *fmt, ...)
{
va_list args;
if (log_level == 0 || log_len >= log_size - 1)
return;
va_start(args, fmt);
log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
va_end(args);
}
/* string representation of 'enum bpf_reg_type' */
static const char * const reg_type_str[] = {
[NOT_INIT] = "?",
[UNKNOWN_VALUE] = "inv",
[PTR_TO_CTX] = "ctx",
[CONST_PTR_TO_MAP] = "map_ptr",
[PTR_TO_MAP_VALUE] = "map_value",
[PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
[PTR_TO_MAP_VALUE_ADJ] = "map_value_adj",
[FRAME_PTR] = "fp",
[PTR_TO_STACK] = "fp",
[CONST_IMM] = "imm",
[PTR_TO_PACKET] = "pkt",
[PTR_TO_PACKET_END] = "pkt_end",
};
#define __BPF_FUNC_STR_FN(x) [BPF_FUNC_ ## x] = __stringify(bpf_ ## x)
static const char * const func_id_str[] = {
__BPF_FUNC_MAPPER(__BPF_FUNC_STR_FN)
};
#undef __BPF_FUNC_STR_FN
static const char *func_id_name(int id)
{
BUILD_BUG_ON(ARRAY_SIZE(func_id_str) != __BPF_FUNC_MAX_ID);
if (id >= 0 && id < __BPF_FUNC_MAX_ID && func_id_str[id])
return func_id_str[id];
else
return "unknown";
}
static void print_verifier_state(struct bpf_verifier_state *state)
{
struct bpf_reg_state *reg;
enum bpf_reg_type t;
int i;
for (i = 0; i < MAX_BPF_REG; i++) {
reg = &state->regs[i];
t = reg->type;
if (t == NOT_INIT)
continue;
verbose(" R%d=%s", i, reg_type_str[t]);
if (t == CONST_IMM || t == PTR_TO_STACK)
verbose("%lld", reg->imm);
else if (t == PTR_TO_PACKET)
verbose("(id=%d,off=%d,r=%d)",
reg->id, reg->off, reg->range);
else if (t == UNKNOWN_VALUE && reg->imm)
verbose("%lld", reg->imm);
else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
t == PTR_TO_MAP_VALUE_OR_NULL ||
t == PTR_TO_MAP_VALUE_ADJ)
verbose("(ks=%d,vs=%d,id=%u)",
reg->map_ptr->key_size,
reg->map_ptr->value_size,
reg->id);
if (reg->min_value != BPF_REGISTER_MIN_RANGE)
verbose(",min_value=%lld",
(long long)reg->min_value);
if (reg->max_value != BPF_REGISTER_MAX_RANGE)
verbose(",max_value=%llu",
(unsigned long long)reg->max_value);
if (reg->min_align)
verbose(",min_align=%u", reg->min_align);
if (reg->aux_off)
verbose(",aux_off=%u", reg->aux_off);
if (reg->aux_off_align)
verbose(",aux_off_align=%u", reg->aux_off_align);
}
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] == STACK_SPILL)
verbose(" fp%d=%s", -MAX_BPF_STACK + i,
reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]);
}
verbose("\n");
}
static const char *const bpf_class_string[] = {
[BPF_LD] = "ld",
[BPF_LDX] = "ldx",
[BPF_ST] = "st",
[BPF_STX] = "stx",
[BPF_ALU] = "alu",
[BPF_JMP] = "jmp",
[BPF_RET] = "BUG",
[BPF_ALU64] = "alu64",
};
static const char *const bpf_alu_string[16] = {
[BPF_ADD >> 4] = "+=",
[BPF_SUB >> 4] = "-=",
[BPF_MUL >> 4] = "*=",
[BPF_DIV >> 4] = "/=",
[BPF_OR >> 4] = "|=",
[BPF_AND >> 4] = "&=",
[BPF_LSH >> 4] = "<<=",
[BPF_RSH >> 4] = ">>=",
[BPF_NEG >> 4] = "neg",
[BPF_MOD >> 4] = "%=",
[BPF_XOR >> 4] = "^=",
[BPF_MOV >> 4] = "=",
[BPF_ARSH >> 4] = "s>>=",
[BPF_END >> 4] = "endian",
};
static const char *const bpf_ldst_string[] = {
[BPF_W >> 3] = "u32",
[BPF_H >> 3] = "u16",
[BPF_B >> 3] = "u8",
[BPF_DW >> 3] = "u64",
};
static const char *const bpf_jmp_string[16] = {
[BPF_JA >> 4] = "jmp",
[BPF_JEQ >> 4] = "==",
[BPF_JGT >> 4] = ">",
[BPF_JGE >> 4] = ">=",
[BPF_JSET >> 4] = "&",
[BPF_JNE >> 4] = "!=",
[BPF_JSGT >> 4] = "s>",
[BPF_JSGE >> 4] = "s>=",
[BPF_CALL >> 4] = "call",
[BPF_EXIT >> 4] = "exit",
};
static void print_bpf_insn(const struct bpf_verifier_env *env,
const struct bpf_insn *insn)
{
u8 class = BPF_CLASS(insn->code);
if (class == BPF_ALU || class == BPF_ALU64) {
if (BPF_SRC(insn->code) == BPF_X)
verbose("(%02x) %sr%d %s %sr%d\n",
insn->code, class == BPF_ALU ? "(u32) " : "",
insn->dst_reg,
bpf_alu_string[BPF_OP(insn->code) >> 4],
class == BPF_ALU ? "(u32) " : "",
insn->src_reg);
else
verbose("(%02x) %sr%d %s %s%d\n",
insn->code, class == BPF_ALU ? "(u32) " : "",
insn->dst_reg,
bpf_alu_string[BPF_OP(insn->code) >> 4],
class == BPF_ALU ? "(u32) " : "",
insn->imm);
} else if (class == BPF_STX) {
if (BPF_MODE(insn->code) == BPF_MEM)
verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg,
insn->off, insn->src_reg);
else if (BPF_MODE(insn->code) == BPF_XADD)
verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg, insn->off,
insn->src_reg);
else
verbose("BUG_%02x\n", insn->code);
} else if (class == BPF_ST) {
if (BPF_MODE(insn->code) != BPF_MEM) {
verbose("BUG_st_%02x\n", insn->code);
return;
}
verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg,
insn->off, insn->imm);
} else if (class == BPF_LDX) {
if (BPF_MODE(insn->code) != BPF_MEM) {
verbose("BUG_ldx_%02x\n", insn->code);
return;
}
verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
insn->code, insn->dst_reg,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->src_reg, insn->off);
} else if (class == BPF_LD) {
if (BPF_MODE(insn->code) == BPF_ABS) {
verbose("(%02x) r0 = *(%s *)skb[%d]\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->imm);
} else if (BPF_MODE(insn->code) == BPF_IND) {
verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->src_reg, insn->imm);
} else if (BPF_MODE(insn->code) == BPF_IMM &&
BPF_SIZE(insn->code) == BPF_DW) {
/* At this point, we already made sure that the second
* part of the ldimm64 insn is accessible.
*/
u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
bool map_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD;
if (map_ptr && !env->allow_ptr_leaks)
imm = 0;
verbose("(%02x) r%d = 0x%llx\n", insn->code,
insn->dst_reg, (unsigned long long)imm);
} else {
verbose("BUG_ld_%02x\n", insn->code);
return;
}
} else if (class == BPF_JMP) {
u8 opcode = BPF_OP(insn->code);
if (opcode == BPF_CALL) {
verbose("(%02x) call %s#%d\n", insn->code,
func_id_name(insn->imm), insn->imm);
} else if (insn->code == (BPF_JMP | BPF_JA)) {
verbose("(%02x) goto pc%+d\n",
insn->code, insn->off);
} else if (insn->code == (BPF_JMP | BPF_EXIT)) {
verbose("(%02x) exit\n", insn->code);
} else if (BPF_SRC(insn->code) == BPF_X) {
verbose("(%02x) if r%d %s r%d goto pc%+d\n",
insn->code, insn->dst_reg,
bpf_jmp_string[BPF_OP(insn->code) >> 4],
insn->src_reg, insn->off);
} else {
verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
insn->code, insn->dst_reg,
bpf_jmp_string[BPF_OP(insn->code) >> 4],
insn->imm, insn->off);
}
} else {
verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
}
}
static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx)
{
struct bpf_verifier_stack_elem *elem;
int insn_idx;
if (env->head == NULL)
return -1;
memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
insn_idx = env->head->insn_idx;
if (prev_insn_idx)
*prev_insn_idx = env->head->prev_insn_idx;
elem = env->head->next;
kfree(env->head);
env->head = elem;
env->stack_size--;
return insn_idx;
}
static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx)
{
struct bpf_verifier_stack_elem *elem;
elem = kmalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL);
if (!elem)
goto err;
memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
elem->insn_idx = insn_idx;
elem->prev_insn_idx = prev_insn_idx;
elem->next = env->head;
env->head = elem;
env->stack_size++;
if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
verbose("BPF program is too complex\n");
goto err;
}
return &elem->st;
err:
/* pop all elements and return */
while (pop_stack(env, NULL) >= 0);
return NULL;
}
#define CALLER_SAVED_REGS 6
static const int caller_saved[CALLER_SAVED_REGS] = {
BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
};
static void mark_reg_not_init(struct bpf_reg_state *regs, u32 regno)
{
BUG_ON(regno >= MAX_BPF_REG);
memset(&regs[regno], 0, sizeof(regs[regno]));
regs[regno].type = NOT_INIT;
regs[regno].min_value = BPF_REGISTER_MIN_RANGE;
regs[regno].max_value = BPF_REGISTER_MAX_RANGE;
}
static void init_reg_state(struct bpf_reg_state *regs)
{
int i;
for (i = 0; i < MAX_BPF_REG; i++)
mark_reg_not_init(regs, i);
/* frame pointer */
regs[BPF_REG_FP].type = FRAME_PTR;
/* 1st arg to a function */
regs[BPF_REG_1].type = PTR_TO_CTX;
}
static void __mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno)
{
regs[regno].type = UNKNOWN_VALUE;
regs[regno].id = 0;
regs[regno].imm = 0;
}
static void mark_reg_unknown_value(struct bpf_reg_state *regs, u32 regno)
{
BUG_ON(regno >= MAX_BPF_REG);
__mark_reg_unknown_value(regs, regno);
}
static void reset_reg_range_values(struct bpf_reg_state *regs, u32 regno)
{
regs[regno].min_value = BPF_REGISTER_MIN_RANGE;
regs[regno].max_value = BPF_REGISTER_MAX_RANGE;
regs[regno].value_from_signed = false;
regs[regno].min_align = 0;
}
static void mark_reg_unknown_value_and_range(struct bpf_reg_state *regs,
u32 regno)
{
mark_reg_unknown_value(regs, regno);
reset_reg_range_values(regs, regno);
}
enum reg_arg_type {
SRC_OP, /* register is used as source operand */
DST_OP, /* register is used as destination operand */
DST_OP_NO_MARK /* same as above, check only, don't mark */
};
static int check_reg_arg(struct bpf_reg_state *regs, u32 regno,
enum reg_arg_type t)
{
if (regno >= MAX_BPF_REG) {
verbose("R%d is invalid\n", regno);
return -EINVAL;
}
if (t == SRC_OP) {
/* check whether register used as source operand can be read */
if (regs[regno].type == NOT_INIT) {
verbose("R%d !read_ok\n", regno);
return -EACCES;
}
} else {
/* check whether register used as dest operand can be written to */
if (regno == BPF_REG_FP) {
verbose("frame pointer is read only\n");
return -EACCES;
}
if (t == DST_OP)
mark_reg_unknown_value(regs, regno);
}
return 0;
}
static bool is_spillable_regtype(enum bpf_reg_type type)
{
switch (type) {
case PTR_TO_MAP_VALUE:
case PTR_TO_MAP_VALUE_OR_NULL:
case PTR_TO_MAP_VALUE_ADJ:
case PTR_TO_STACK:
case PTR_TO_CTX:
case PTR_TO_PACKET:
case PTR_TO_PACKET_END:
case FRAME_PTR:
case CONST_PTR_TO_MAP:
return true;
default:
return false;
}
}
/* check_stack_read/write functions track spill/fill of registers,
* stack boundary and alignment are checked in check_mem_access()
*/
static int check_stack_write(struct bpf_verifier_state *state, int off,
int size, int value_regno)
{
int i;
/* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
* so it's aligned access and [off, off + size) are within stack limits
*/
if (value_regno >= 0 &&
is_spillable_regtype(state->regs[value_regno].type)) {
/* register containing pointer is being spilled into stack */
if (size != BPF_REG_SIZE) {
verbose("invalid size of register spill\n");
return -EACCES;
}
/* save register state */
state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
state->regs[value_regno];
for (i = 0; i < BPF_REG_SIZE; i++)
state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
} else {
/* regular write of data into stack */
state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
(struct bpf_reg_state) {};
for (i = 0; i < size; i++)
state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
}
return 0;
}
static int check_stack_read(struct bpf_verifier_state *state, int off, int size,
int value_regno)
{
u8 *slot_type;
int i;
slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
if (slot_type[0] == STACK_SPILL) {
if (size != BPF_REG_SIZE) {
verbose("invalid size of register spill\n");
return -EACCES;
}
for (i = 1; i < BPF_REG_SIZE; i++) {
if (slot_type[i] != STACK_SPILL) {
verbose("corrupted spill memory\n");
return -EACCES;
}
}
if (value_regno >= 0)
/* restore register state from stack */
state->regs[value_regno] =
state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
return 0;
} else {
for (i = 0; i < size; i++) {
if (slot_type[i] != STACK_MISC) {
verbose("invalid read from stack off %d+%d size %d\n",
off, i, size);
return -EACCES;
}
}
if (value_regno >= 0)
/* have read misc data from the stack */
mark_reg_unknown_value_and_range(state->regs,
value_regno);
return 0;
}
}
/* check read/write into map element returned by bpf_map_lookup_elem() */
static int check_map_access(struct bpf_verifier_env *env, u32 regno, int off,
int size)
{
struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
if (off < 0 || size <= 0 || off + size > map->value_size) {
verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
map->value_size, off, size);
return -EACCES;
}
return 0;
}
/* check read/write into an adjusted map element */
static int check_map_access_adj(struct bpf_verifier_env *env, u32 regno,
int off, int size)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_reg_state *reg = &state->regs[regno];
int err;
/* We adjusted the register to this map value, so we
* need to change off and size to min_value and max_value
* respectively to make sure our theoretical access will be
* safe.
*/
if (log_level)
print_verifier_state(state);
env->varlen_map_value_access = true;
/* The minimum value is only important with signed
* comparisons where we can't assume the floor of a
* value is 0. If we are using signed variables for our
* index'es we need to make sure that whatever we use
* will have a set floor within our range.
*/
if (reg->min_value < 0) {
verbose("R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
regno);
return -EACCES;
}
err = check_map_access(env, regno, reg->min_value + off, size);
if (err) {
verbose("R%d min value is outside of the array range\n",
regno);
return err;
}
/* If we haven't set a max value then we need to bail
* since we can't be sure we won't do bad things.
*/
if (reg->max_value == BPF_REGISTER_MAX_RANGE) {
verbose("R%d unbounded memory access, make sure to bounds check any array access into a map\n",
regno);
return -EACCES;
}
return check_map_access(env, regno, reg->max_value + off, size);
}
#define MAX_PACKET_OFF 0xffff
static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
const struct bpf_call_arg_meta *meta,
enum bpf_access_type t)
{
switch (env->prog->type) {
case BPF_PROG_TYPE_LWT_IN:
case BPF_PROG_TYPE_LWT_OUT:
/* dst_input() and dst_output() can't write for now */
if (t == BPF_WRITE)
return false;
/* fallthrough */
case BPF_PROG_TYPE_SCHED_CLS:
case BPF_PROG_TYPE_SCHED_ACT:
case BPF_PROG_TYPE_XDP:
case BPF_PROG_TYPE_LWT_XMIT:
if (meta)
return meta->pkt_access;
env->seen_direct_write = true;
return true;
default:
return false;
}
}
static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
int size)
{
struct bpf_reg_state *regs = env->cur_state.regs;
struct bpf_reg_state *reg = &regs[regno];
off += reg->off;
if (off < 0 || size <= 0 || off + size > reg->range) {
verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
off, size, regno, reg->id, reg->off, reg->range);
return -EACCES;
}
return 0;
}
/* check access to 'struct bpf_context' fields */
static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size,
enum bpf_access_type t, enum bpf_reg_type *reg_type)
{
struct bpf_insn_access_aux info = {
.reg_type = *reg_type,
};
/* for analyzer ctx accesses are already validated and converted */
if (env->analyzer_ops)
return 0;
if (env->prog->aux->ops->is_valid_access &&
env->prog->aux->ops->is_valid_access(off, size, t, &info)) {
/* A non zero info.ctx_field_size indicates that this field is a
* candidate for later verifier transformation to load the whole
* field and then apply a mask when accessed with a narrower
* access than actual ctx access size. A zero info.ctx_field_size
* will only allow for whole field access and rejects any other
* type of narrower access.
*/
env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size;
*reg_type = info.reg_type;
/* remember the offset of last byte accessed in ctx */
if (env->prog->aux->max_ctx_offset < off + size)
env->prog->aux->max_ctx_offset = off + size;
return 0;
}
verbose("invalid bpf_context access off=%d size=%d\n", off, size);
return -EACCES;
}
static bool __is_pointer_value(bool allow_ptr_leaks,
const struct bpf_reg_state *reg)
{
if (allow_ptr_leaks)
return false;
switch (reg->type) {
case UNKNOWN_VALUE:
case CONST_IMM:
return false;
default:
return true;
}
}
static bool is_pointer_value(struct bpf_verifier_env *env, int regno)
{
return __is_pointer_value(env->allow_ptr_leaks, &env->cur_state.regs[regno]);
}
static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg,
int off, int size, bool strict)
{
int ip_align;
int reg_off;
/* Byte size accesses are always allowed. */
if (!strict || size == 1)
return 0;
reg_off = reg->off;
if (reg->id) {
if (reg->aux_off_align % size) {
verbose("Packet access is only %u byte aligned, %d byte access not allowed\n",
reg->aux_off_align, size);
return -EACCES;
}
reg_off += reg->aux_off;
}
/* For platforms that do not have a Kconfig enabling
* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of
* NET_IP_ALIGN is universally set to '2'. And on platforms
* that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get
* to this code only in strict mode where we want to emulate
* the NET_IP_ALIGN==2 checking. Therefore use an
* unconditional IP align value of '2'.
*/
ip_align = 2;
if ((ip_align + reg_off + off) % size != 0) {
verbose("misaligned packet access off %d+%d+%d size %d\n",
ip_align, reg_off, off, size);
return -EACCES;
}
return 0;
}
static int check_val_ptr_alignment(const struct bpf_reg_state *reg,
int size, bool strict)
{
if (strict && size != 1) {
verbose("Unknown alignment. Only byte-sized access allowed in value access.\n");
return -EACCES;
}
return 0;
}
static int check_ptr_alignment(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
int off, int size)
{
bool strict = env->strict_alignment;
switch (reg->type) {
case PTR_TO_PACKET:
return check_pkt_ptr_alignment(reg, off, size, strict);
case PTR_TO_MAP_VALUE_ADJ:
return check_val_ptr_alignment(reg, size, strict);
default:
if (off % size != 0) {
verbose("misaligned access off %d size %d\n",
off, size);
return -EACCES;
}
return 0;
}
}
/* check whether memory at (regno + off) is accessible for t = (read | write)
* if t==write, value_regno is a register which value is stored into memory
* if t==read, value_regno is a register which will receive the value from memory
* if t==write && value_regno==-1, some unknown value is stored into memory
* if t==read && value_regno==-1, don't care what we read from memory
*/
static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regno, int off,
int bpf_size, enum bpf_access_type t,
int value_regno)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_reg_state *reg = &state->regs[regno];
int size, err = 0;
if (reg->type == PTR_TO_STACK)
off += reg->imm;
size = bpf_size_to_bytes(bpf_size);
if (size < 0)
return size;
err = check_ptr_alignment(env, reg, off, size);
if (err)
return err;
if (reg->type == PTR_TO_MAP_VALUE ||
reg->type == PTR_TO_MAP_VALUE_ADJ) {
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose("R%d leaks addr into map\n", value_regno);
return -EACCES;
}
if (reg->type == PTR_TO_MAP_VALUE_ADJ)
err = check_map_access_adj(env, regno, off, size);
else
err = check_map_access(env, regno, off, size);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown_value_and_range(state->regs,
value_regno);
} else if (reg->type == PTR_TO_CTX) {
enum bpf_reg_type reg_type = UNKNOWN_VALUE;
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose("R%d leaks addr into ctx\n", value_regno);
return -EACCES;
}
err = check_ctx_access(env, insn_idx, off, size, t, &reg_type);
if (!err && t == BPF_READ && value_regno >= 0) {
mark_reg_unknown_value_and_range(state->regs,
value_regno);
/* note that reg.[id|off|range] == 0 */
state->regs[value_regno].type = reg_type;
state->regs[value_regno].aux_off = 0;
state->regs[value_regno].aux_off_align = 0;
}
} else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) {
if (off >= 0 || off < -MAX_BPF_STACK) {
verbose("invalid stack off=%d size=%d\n", off, size);
return -EACCES;
}
if (env->prog->aux->stack_depth < -off)
env->prog->aux->stack_depth = -off;
if (t == BPF_WRITE) {
if (!env->allow_ptr_leaks &&
state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL &&
size != BPF_REG_SIZE) {
verbose("attempt to corrupt spilled pointer on stack\n");
return -EACCES;
}
err = check_stack_write(state, off, size, value_regno);
} else {
err = check_stack_read(state, off, size, value_regno);
}
} else if (state->regs[regno].type == PTR_TO_PACKET) {
if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) {
verbose("cannot write into packet\n");
return -EACCES;
}
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose("R%d leaks addr into packet\n", value_regno);
return -EACCES;
}
err = check_packet_access(env, regno, off, size);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown_value_and_range(state->regs,
value_regno);
} else {
verbose("R%d invalid mem access '%s'\n",
regno, reg_type_str[reg->type]);
return -EACCES;
}
if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks &&
state->regs[value_regno].type == UNKNOWN_VALUE) {
/* 1 or 2 byte load zero-extends, determine the number of
* zero upper bits. Not doing it fo 4 byte load, since
* such values cannot be added to ptr_to_packet anyway.
*/
state->regs[value_regno].imm = 64 - size * 8;
}
return err;
}
static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
int err;
if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
insn->imm != 0) {
verbose("BPF_XADD uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
return err;
/* check src2 operand */
err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->src_reg)) {
verbose("R%d leaks addr into mem\n", insn->src_reg);
return -EACCES;
}
/* check whether atomic_add can read the memory */
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_READ, -1);
if (err)
return err;
/* check whether atomic_add can write into the same memory */
return check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_WRITE, -1);
}
/* when register 'regno' is passed into function that will read 'access_size'
* bytes from that pointer, make sure that it's within stack boundary
* and all elements of stack are initialized
*/
static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
int access_size, bool zero_size_allowed,
struct bpf_call_arg_meta *meta)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_reg_state *regs = state->regs;
int off, i;
if (regs[regno].type != PTR_TO_STACK) {
if (zero_size_allowed && access_size == 0 &&
regs[regno].type == CONST_IMM &&
regs[regno].imm == 0)
return 0;
verbose("R%d type=%s expected=%s\n", regno,
reg_type_str[regs[regno].type],
reg_type_str[PTR_TO_STACK]);
return -EACCES;
}
off = regs[regno].imm;
if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
access_size <= 0) {
verbose("invalid stack type R%d off=%d access_size=%d\n",
regno, off, access_size);
return -EACCES;
}
if (env->prog->aux->stack_depth < -off)
env->prog->aux->stack_depth = -off;
if (meta && meta->raw_mode) {
meta->access_size = access_size;
meta->regno = regno;
return 0;
}
for (i = 0; i < access_size; i++) {
if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
verbose("invalid indirect read from stack off %d+%d size %d\n",
off, i, access_size);
return -EACCES;
}
}
return 0;
}
static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
int access_size, bool zero_size_allowed,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *regs = env->cur_state.regs;
switch (regs[regno].type) {
case PTR_TO_PACKET:
return check_packet_access(env, regno, 0, access_size);
case PTR_TO_MAP_VALUE:
return check_map_access(env, regno, 0, access_size);
case PTR_TO_MAP_VALUE_ADJ:
return check_map_access_adj(env, regno, 0, access_size);
default: /* const_imm|ptr_to_stack or invalid ptr */
return check_stack_boundary(env, regno, access_size,
zero_size_allowed, meta);
}
}
static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
enum bpf_arg_type arg_type,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *regs = env->cur_state.regs, *reg = &regs[regno];
enum bpf_reg_type expected_type, type = reg->type;
int err = 0;
if (arg_type == ARG_DONTCARE)
return 0;
if (type == NOT_INIT) {
verbose("R%d !read_ok\n", regno);
return -EACCES;
}
if (arg_type == ARG_ANYTHING) {
if (is_pointer_value(env, regno)) {
verbose("R%d leaks addr into helper function\n", regno);
return -EACCES;
}
return 0;
}
if (type == PTR_TO_PACKET &&
!may_access_direct_pkt_data(env, meta, BPF_READ)) {
verbose("helper access to the packet is not allowed\n");
return -EACCES;
}
if (arg_type == ARG_PTR_TO_MAP_KEY ||
arg_type == ARG_PTR_TO_MAP_VALUE) {
expected_type = PTR_TO_STACK;
if (type != PTR_TO_PACKET && type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_SIZE ||
arg_type == ARG_CONST_SIZE_OR_ZERO) {
expected_type = CONST_IMM;
/* One exception. Allow UNKNOWN_VALUE registers when the
* boundaries are known and don't cause unsafe memory accesses
*/
if (type != UNKNOWN_VALUE && type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_MAP_PTR) {
expected_type = CONST_PTR_TO_MAP;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_CTX) {
expected_type = PTR_TO_CTX;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_MEM ||
arg_type == ARG_PTR_TO_UNINIT_MEM) {
expected_type = PTR_TO_STACK;
/* One exception here. In case function allows for NULL to be
* passed in as argument, it's a CONST_IMM type. Final test
* happens during stack boundary checking.
*/
if (type == CONST_IMM && reg->imm == 0)
/* final test in check_stack_boundary() */;
else if (type != PTR_TO_PACKET && type != PTR_TO_MAP_VALUE &&
type != PTR_TO_MAP_VALUE_ADJ && type != expected_type)
goto err_type;
meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM;
} else {
verbose("unsupported arg_type %d\n", arg_type);
return -EFAULT;
}
if (arg_type == ARG_CONST_MAP_PTR) {
/* bpf_map_xxx(map_ptr) call: remember that map_ptr */
meta->map_ptr = reg->map_ptr;
} else if (arg_type == ARG_PTR_TO_MAP_KEY) {
/* bpf_map_xxx(..., map_ptr, ..., key) call:
* check that [key, key + map->key_size) are within
* stack limits and initialized
*/
if (!meta->map_ptr) {
/* in function declaration map_ptr must come before
* map_key, so that it's verified and known before
* we have to check map_key here. Otherwise it means
* that kernel subsystem misconfigured verifier
*/
verbose("invalid map_ptr to access map->key\n");
return -EACCES;
}
if (type == PTR_TO_PACKET)
err = check_packet_access(env, regno, 0,
meta->map_ptr->key_size);
else
err = check_stack_boundary(env, regno,
meta->map_ptr->key_size,
false, NULL);
} else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
/* bpf_map_xxx(..., map_ptr, ..., value) call:
* check [value, value + map->value_size) validity
*/
if (!meta->map_ptr) {
/* kernel subsystem misconfigured verifier */
verbose("invalid map_ptr to access map->value\n");
return -EACCES;
}
if (type == PTR_TO_PACKET)
err = check_packet_access(env, regno, 0,
meta->map_ptr->value_size);
else
err = check_stack_boundary(env, regno,
meta->map_ptr->value_size,
false, NULL);
} else if (arg_type == ARG_CONST_SIZE ||
arg_type == ARG_CONST_SIZE_OR_ZERO) {
bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
/* bpf_xxx(..., buf, len) call will access 'len' bytes
* from stack pointer 'buf'. Check it
* note: regno == len, regno - 1 == buf
*/
if (regno == 0) {
/* kernel subsystem misconfigured verifier */
verbose("ARG_CONST_SIZE cannot be first argument\n");
return -EACCES;
}
/* If the register is UNKNOWN_VALUE, the access check happens
* using its boundaries. Otherwise, just use its imm
*/
if (type == UNKNOWN_VALUE) {
/* For unprivileged variable accesses, disable raw
* mode so that the program is required to
* initialize all the memory that the helper could
* just partially fill up.
*/
meta = NULL;
if (reg->min_value < 0) {
verbose("R%d min value is negative, either use unsigned or 'var &= const'\n",
regno);
return -EACCES;
}
if (reg->min_value == 0) {
err = check_helper_mem_access(env, regno - 1, 0,
zero_size_allowed,
meta);
if (err)
return err;
}
if (reg->max_value == BPF_REGISTER_MAX_RANGE) {
verbose("R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n",
regno);
return -EACCES;
}
err = check_helper_mem_access(env, regno - 1,
reg->max_value,
zero_size_allowed, meta);
if (err)
return err;
} else {
/* register is CONST_IMM */
err = check_helper_mem_access(env, regno - 1, reg->imm,
zero_size_allowed, meta);
}
}
return err;
err_type:
verbose("R%d type=%s expected=%s\n", regno,
reg_type_str[type], reg_type_str[expected_type]);
return -EACCES;
}
static int check_map_func_compatibility(struct bpf_map *map, int func_id)
{
if (!map)
return 0;
/* We need a two way check, first is from map perspective ... */
switch (map->map_type) {
case BPF_MAP_TYPE_PROG_ARRAY:
if (func_id != BPF_FUNC_tail_call)
goto error;
break;
case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
if (func_id != BPF_FUNC_perf_event_read &&
func_id != BPF_FUNC_perf_event_output)
goto error;
break;
case BPF_MAP_TYPE_STACK_TRACE:
if (func_id != BPF_FUNC_get_stackid)
goto error;
break;
case BPF_MAP_TYPE_CGROUP_ARRAY:
if (func_id != BPF_FUNC_skb_under_cgroup &&
func_id != BPF_FUNC_current_task_under_cgroup)
goto error;
break;
case BPF_MAP_TYPE_ARRAY_OF_MAPS:
case BPF_MAP_TYPE_HASH_OF_MAPS:
if (func_id != BPF_FUNC_map_lookup_elem)
goto error;
default:
break;
}
/* ... and second from the function itself. */
switch (func_id) {
case BPF_FUNC_tail_call:
if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
goto error;
break;
case BPF_FUNC_perf_event_read:
case BPF_FUNC_perf_event_output:
if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
goto error;
break;
case BPF_FUNC_get_stackid:
if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
goto error;
break;
case BPF_FUNC_current_task_under_cgroup:
case BPF_FUNC_skb_under_cgroup:
if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
goto error;
break;
default:
break;
}
return 0;
error:
verbose("cannot pass map_type %d into func %s#%d\n",
map->map_type, func_id_name(func_id), func_id);
return -EINVAL;
}
static int check_raw_mode(const struct bpf_func_proto *fn)
{
int count = 0;
if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM)
count++;
return count > 1 ? -EINVAL : 0;
}
static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_reg_state *regs = state->regs, *reg;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
if (regs[i].type == PTR_TO_PACKET ||
regs[i].type == PTR_TO_PACKET_END)
mark_reg_unknown_value(regs, i);
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] != STACK_SPILL)
continue;
reg = &state->spilled_regs[i / BPF_REG_SIZE];
if (reg->type != PTR_TO_PACKET &&
reg->type != PTR_TO_PACKET_END)
continue;
__mark_reg_unknown_value(state->spilled_regs,
i / BPF_REG_SIZE);
}
}
static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
{
struct bpf_verifier_state *state = &env->cur_state;
const struct bpf_func_proto *fn = NULL;
struct bpf_reg_state *regs = state->regs;
struct bpf_call_arg_meta meta;
bool changes_data;
int i, err;
/* find function prototype */
if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
verbose("invalid func %s#%d\n", func_id_name(func_id), func_id);
return -EINVAL;
}
if (env->prog->aux->ops->get_func_proto)
fn = env->prog->aux->ops->get_func_proto(func_id);
if (!fn) {
verbose("unknown func %s#%d\n", func_id_name(func_id), func_id);
return -EINVAL;
}
/* eBPF programs must be GPL compatible to use GPL-ed functions */
if (!env->prog->gpl_compatible && fn->gpl_only) {
verbose("cannot call GPL only function from proprietary program\n");
return -EINVAL;
}
changes_data = bpf_helper_changes_pkt_data(fn->func);
memset(&meta, 0, sizeof(meta));
meta.pkt_access = fn->pkt_access;
/* We only support one arg being in raw mode at the moment, which
* is sufficient for the helper functions we have right now.
*/
err = check_raw_mode(fn);
if (err) {
verbose("kernel subsystem misconfigured func %s#%d\n",
func_id_name(func_id), func_id);
return err;
}
/* check args */
err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
if (err)
return err;
/* Mark slots with STACK_MISC in case of raw mode, stack offset
* is inferred from register state.
*/
for (i = 0; i < meta.access_size; i++) {
err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B, BPF_WRITE, -1);
if (err)
return err;
}
/* reset caller saved regs */
for (i = 0; i < CALLER_SAVED_REGS; i++)
mark_reg_not_init(regs, caller_saved[i]);
/* update return register */
if (fn->ret_type == RET_INTEGER) {
regs[BPF_REG_0].type = UNKNOWN_VALUE;
} else if (fn->ret_type == RET_VOID) {
regs[BPF_REG_0].type = NOT_INIT;
} else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
struct bpf_insn_aux_data *insn_aux;
regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
regs[BPF_REG_0].max_value = regs[BPF_REG_0].min_value = 0;
/* remember map_ptr, so that check_map_access()
* can check 'value_size' boundary of memory access
* to map element returned from bpf_map_lookup_elem()
*/
if (meta.map_ptr == NULL) {
verbose("kernel subsystem misconfigured verifier\n");
return -EINVAL;
}
regs[BPF_REG_0].map_ptr = meta.map_ptr;
regs[BPF_REG_0].id = ++env->id_gen;
insn_aux = &env->insn_aux_data[insn_idx];
if (!insn_aux->map_ptr)
insn_aux->map_ptr = meta.map_ptr;
else if (insn_aux->map_ptr != meta.map_ptr)
insn_aux->map_ptr = BPF_MAP_PTR_POISON;
} else {
verbose("unknown return type %d of func %s#%d\n",
fn->ret_type, func_id_name(func_id), func_id);
return -EINVAL;
}
err = check_map_func_compatibility(meta.map_ptr, func_id);
if (err)
return err;
if (changes_data)
clear_all_pkt_pointers(env);
return 0;
}
static int check_packet_ptr_add(struct bpf_verifier_env *env,
struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
struct bpf_reg_state *dst_reg = &regs[insn->dst_reg];
struct bpf_reg_state *src_reg = &regs[insn->src_reg];
struct bpf_reg_state tmp_reg;
s32 imm;
if (BPF_SRC(insn->code) == BPF_K) {
/* pkt_ptr += imm */
imm = insn->imm;
add_imm:
if (imm < 0) {
verbose("addition of negative constant to packet pointer is not allowed\n");
return -EACCES;
}
if (imm >= MAX_PACKET_OFF ||
imm + dst_reg->off >= MAX_PACKET_OFF) {
verbose("constant %d is too large to add to packet pointer\n",
imm);
return -EACCES;
}
/* a constant was added to pkt_ptr.
* Remember it while keeping the same 'id'
*/
dst_reg->off += imm;
} else {
bool had_id;
if (src_reg->type == PTR_TO_PACKET) {
/* R6=pkt(id=0,off=0,r=62) R7=imm22; r7 += r6 */
tmp_reg = *dst_reg; /* save r7 state */
*dst_reg = *src_reg; /* copy pkt_ptr state r6 into r7 */
src_reg = &tmp_reg; /* pretend it's src_reg state */
/* if the checks below reject it, the copy won't matter,
* since we're rejecting the whole program. If all ok,
* then imm22 state will be added to r7
* and r7 will be pkt(id=0,off=22,r=62) while
* r6 will stay as pkt(id=0,off=0,r=62)
*/
}
if (src_reg->type == CONST_IMM) {
/* pkt_ptr += reg where reg is known constant */
imm = src_reg->imm;
goto add_imm;
}
/* disallow pkt_ptr += reg
* if reg is not uknown_value with guaranteed zero upper bits
* otherwise pkt_ptr may overflow and addition will become
* subtraction which is not allowed
*/
if (src_reg->type != UNKNOWN_VALUE) {
verbose("cannot add '%s' to ptr_to_packet\n",
reg_type_str[src_reg->type]);
return -EACCES;
}
if (src_reg->imm < 48) {
verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n",
src_reg->imm);
return -EACCES;
}
had_id = (dst_reg->id != 0);
/* dst_reg stays as pkt_ptr type and since some positive
* integer value was added to the pointer, increment its 'id'
*/
dst_reg->id = ++env->id_gen;
/* something was added to pkt_ptr, set range to zero */
dst_reg->aux_off += dst_reg->off;
dst_reg->off = 0;
dst_reg->range = 0;
if (had_id)
dst_reg->aux_off_align = min(dst_reg->aux_off_align,
src_reg->min_align);
else
dst_reg->aux_off_align = src_reg->min_align;
}
return 0;
}
static int evaluate_reg_alu(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
struct bpf_reg_state *dst_reg = &regs[insn->dst_reg];
u8 opcode = BPF_OP(insn->code);
s64 imm_log2;
/* for type == UNKNOWN_VALUE:
* imm > 0 -> number of zero upper bits
* imm == 0 -> don't track which is the same as all bits can be non-zero
*/
if (BPF_SRC(insn->code) == BPF_X) {
struct bpf_reg_state *src_reg = &regs[insn->src_reg];
if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 &&
dst_reg->imm && opcode == BPF_ADD) {
/* dreg += sreg
* where both have zero upper bits. Adding them
* can only result making one more bit non-zero
* in the larger value.
* Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47)
* 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47)
*/
dst_reg->imm = min(dst_reg->imm, src_reg->imm);
dst_reg->imm--;
return 0;
}
if (src_reg->type == CONST_IMM && src_reg->imm > 0 &&
dst_reg->imm && opcode == BPF_ADD) {
/* dreg += sreg
* where dreg has zero upper bits and sreg is const.
* Adding them can only result making one more bit
* non-zero in the larger value.
*/
imm_log2 = __ilog2_u64((long long)src_reg->imm);
dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
dst_reg->imm--;
return 0;
}
/* all other cases non supported yet, just mark dst_reg */
dst_reg->imm = 0;
return 0;
}
/* sign extend 32-bit imm into 64-bit to make sure that
* negative values occupy bit 63. Note ilog2() would have
* been incorrect, since sizeof(insn->imm) == 4
*/
imm_log2 = __ilog2_u64((long long)insn->imm);
if (dst_reg->imm && opcode == BPF_LSH) {
/* reg <<= imm
* if reg was a result of 2 byte load, then its imm == 48
* which means that upper 48 bits are zero and shifting this reg
* left by 4 would mean that upper 44 bits are still zero
*/
dst_reg->imm -= insn->imm;
} else if (dst_reg->imm && opcode == BPF_MUL) {
/* reg *= imm
* if multiplying by 14 subtract 4
* This is conservative calculation of upper zero bits.
* It's not trying to special case insn->imm == 1 or 0 cases
*/
dst_reg->imm -= imm_log2 + 1;
} else if (opcode == BPF_AND) {
/* reg &= imm */
dst_reg->imm = 63 - imm_log2;
} else if (dst_reg->imm && opcode == BPF_ADD) {
/* reg += imm */
dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
dst_reg->imm--;
} else if (opcode == BPF_RSH) {
/* reg >>= imm
* which means that after right shift, upper bits will be zero
* note that verifier already checked that
* 0 <= imm < 64 for shift insn
*/
dst_reg->imm += insn->imm;
if (unlikely(dst_reg->imm > 64))
/* some dumb code did:
* r2 = *(u32 *)mem;
* r2 >>= 32;
* and all bits are zero now */
dst_reg->imm = 64;
} else {
/* all other alu ops, means that we don't know what will
* happen to the value, mark it with unknown number of zero bits
*/
dst_reg->imm = 0;
}
if (dst_reg->imm < 0) {
/* all 64 bits of the register can contain non-zero bits
* and such value cannot be added to ptr_to_packet, since it
* may overflow, mark it as unknown to avoid further eval
*/
dst_reg->imm = 0;
}
return 0;
}
static int evaluate_reg_imm_alu_unknown(struct bpf_verifier_env *env,
struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
struct bpf_reg_state *dst_reg = &regs[insn->dst_reg];
struct bpf_reg_state *src_reg = &regs[insn->src_reg];
u8 opcode = BPF_OP(insn->code);
s64 imm_log2 = __ilog2_u64((long long)dst_reg->imm);
/* BPF_X code with src_reg->type UNKNOWN_VALUE here. */
if (src_reg->imm > 0 && dst_reg->imm) {
switch (opcode) {
case BPF_ADD:
/* dreg += sreg
* where both have zero upper bits. Adding them
* can only result making one more bit non-zero
* in the larger value.
* Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47)
* 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47)
*/
dst_reg->imm = min(src_reg->imm, 63 - imm_log2);
dst_reg->imm--;
break;
case BPF_AND:
/* dreg &= sreg
* AND can not extend zero bits only shrink
* Ex. 0x00..00ffffff
* & 0x0f..ffffffff
* ----------------
* 0x00..00ffffff
*/
dst_reg->imm = max(src_reg->imm, 63 - imm_log2);
break;
case BPF_OR:
/* dreg |= sreg
* OR can only extend zero bits
* Ex. 0x00..00ffffff
* | 0x0f..ffffffff
* ----------------
* 0x0f..00ffffff
*/
dst_reg->imm = min(src_reg->imm, 63 - imm_log2);
break;
case BPF_SUB:
case BPF_MUL:
case BPF_RSH:
case BPF_LSH:
/* These may be flushed out later */
default:
mark_reg_unknown_value(regs, insn->dst_reg);
}
} else {
mark_reg_unknown_value(regs, insn->dst_reg);
}
dst_reg->type = UNKNOWN_VALUE;
return 0;
}
static int evaluate_reg_imm_alu(struct bpf_verifier_env *env,
struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
struct bpf_reg_state *dst_reg = &regs[insn->dst_reg];
struct bpf_reg_state *src_reg = &regs[insn->src_reg];
u8 opcode = BPF_OP(insn->code);
u64 dst_imm = dst_reg->imm;
if (BPF_SRC(insn->code) == BPF_X && src_reg->type == UNKNOWN_VALUE)
return evaluate_reg_imm_alu_unknown(env, insn);
/* dst_reg->type == CONST_IMM here. Simulate execution of insns
* containing ALU ops. Don't care about overflow or negative
* values, just add/sub/... them; registers are in u64.
*/
if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K) {
dst_imm += insn->imm;
} else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X &&
src_reg->type == CONST_IMM) {
dst_imm += src_reg->imm;
} else if (opcode == BPF_SUB && BPF_SRC(insn->code) == BPF_K) {
dst_imm -= insn->imm;
} else if (opcode == BPF_SUB && BPF_SRC(insn->code) == BPF_X &&
src_reg->type == CONST_IMM) {
dst_imm -= src_reg->imm;
} else if (opcode == BPF_MUL && BPF_SRC(insn->code) == BPF_K) {
dst_imm *= insn->imm;
} else if (opcode == BPF_MUL && BPF_SRC(insn->code) == BPF_X &&
src_reg->type == CONST_IMM) {
dst_imm *= src_reg->imm;
} else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_K) {
dst_imm |= insn->imm;
} else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_X &&
src_reg->type == CONST_IMM) {
dst_imm |= src_reg->imm;
} else if (opcode == BPF_AND && BPF_SRC(insn->code) == BPF_K) {
dst_imm &= insn->imm;
} else if (opcode == BPF_AND && BPF_SRC(insn->code) == BPF_X &&
src_reg->type == CONST_IMM) {
dst_imm &= src_reg->imm;
} else if (opcode == BPF_RSH && BPF_SRC(insn->code) == BPF_K) {
dst_imm >>= insn->imm;
} else if (opcode == BPF_RSH && BPF_SRC(insn->code) == BPF_X &&
src_reg->type == CONST_IMM) {
dst_imm >>= src_reg->imm;
} else if (opcode == BPF_LSH && BPF_SRC(insn->code) == BPF_K) {
dst_imm <<= insn->imm;
} else if (opcode == BPF_LSH && BPF_SRC(insn->code) == BPF_X &&
src_reg->type == CONST_IMM) {
dst_imm <<= src_reg->imm;
} else {
mark_reg_unknown_value(regs, insn->dst_reg);
goto out;
}
dst_reg->imm = dst_imm;
out:
return 0;
}
static void check_reg_overflow(struct bpf_reg_state *reg)
{
if (reg->max_value > BPF_REGISTER_MAX_RANGE)
reg->max_value = BPF_REGISTER_MAX_RANGE;
if (reg->min_value < BPF_REGISTER_MIN_RANGE ||
reg->min_value > BPF_REGISTER_MAX_RANGE)
reg->min_value = BPF_REGISTER_MIN_RANGE;
}
static u32 calc_align(u32 imm)
{
if (!imm)
return 1U << 31;
return imm - ((imm - 1) & imm);
}
static void adjust_reg_min_max_vals(struct bpf_verifier_env *env,
struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg;
s64 min_val = BPF_REGISTER_MIN_RANGE;
u64 max_val = BPF_REGISTER_MAX_RANGE;
u8 opcode = BPF_OP(insn->code);
u32 dst_align, src_align;
dst_reg = &regs[insn->dst_reg];
src_align = 0;
if (BPF_SRC(insn->code) == BPF_X) {
check_reg_overflow(&regs[insn->src_reg]);
min_val = regs[insn->src_reg].min_value;
max_val = regs[insn->src_reg].max_value;
/* If the source register is a random pointer then the
* min_value/max_value values represent the range of the known
* accesses into that value, not the actual min/max value of the
* register itself. In this case we have to reset the reg range
* values so we know it is not safe to look at.
*/
if (regs[insn->src_reg].type != CONST_IMM &&
regs[insn->src_reg].type != UNKNOWN_VALUE) {
min_val = BPF_REGISTER_MIN_RANGE;
max_val = BPF_REGISTER_MAX_RANGE;
src_align = 0;
} else {
src_align = regs[insn->src_reg].min_align;
}
} else if (insn->imm < BPF_REGISTER_MAX_RANGE &&
(s64)insn->imm > BPF_REGISTER_MIN_RANGE) {
min_val = max_val = insn->imm;
src_align = calc_align(insn->imm);
}
dst_align = dst_reg->min_align;
/* We don't know anything about what was done to this register, mark it
* as unknown. Also, if both derived bounds came from signed/unsigned
* mixed compares and one side is unbounded, we cannot really do anything
* with them as boundaries cannot be trusted. Thus, arithmetic of two
* regs of such kind will get invalidated bounds on the dst side.
*/
if ((min_val == BPF_REGISTER_MIN_RANGE &&
max_val == BPF_REGISTER_MAX_RANGE) ||
(BPF_SRC(insn->code) == BPF_X &&
((min_val != BPF_REGISTER_MIN_RANGE &&
max_val == BPF_REGISTER_MAX_RANGE) ||
(min_val == BPF_REGISTER_MIN_RANGE &&
max_val != BPF_REGISTER_MAX_RANGE) ||
(dst_reg->min_value != BPF_REGISTER_MIN_RANGE &&
dst_reg->max_value == BPF_REGISTER_MAX_RANGE) ||
(dst_reg->min_value == BPF_REGISTER_MIN_RANGE &&
dst_reg->max_value != BPF_REGISTER_MAX_RANGE)) &&
regs[insn->dst_reg].value_from_signed !=
regs[insn->src_reg].value_from_signed)) {
reset_reg_range_values(regs, insn->dst_reg);
return;
}
/* If one of our values was at the end of our ranges then we can't just
* do our normal operations to the register, we need to set the values
* to the min/max since they are undefined.
*/
if (min_val == BPF_REGISTER_MIN_RANGE)
dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
if (max_val == BPF_REGISTER_MAX_RANGE)
dst_reg->max_value = BPF_REGISTER_MAX_RANGE;
switch (opcode) {
case BPF_ADD:
if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
dst_reg->min_value += min_val;
if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
dst_reg->max_value += max_val;
dst_reg->min_align = min(src_align, dst_align);
break;
case BPF_SUB:
if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
dst_reg->min_value -= min_val;
if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
dst_reg->max_value -= max_val;
dst_reg->min_align = min(src_align, dst_align);
break;
case BPF_MUL:
if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
dst_reg->min_value *= min_val;
if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
dst_reg->max_value *= max_val;
dst_reg->min_align = max(src_align, dst_align);
break;
case BPF_AND:
/* Disallow AND'ing of negative numbers, ain't nobody got time
* for that. Otherwise the minimum is 0 and the max is the max
* value we could AND against.
*/
if (min_val < 0)
dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
else
dst_reg->min_value = 0;
dst_reg->max_value = max_val;
dst_reg->min_align = max(src_align, dst_align);
break;
case BPF_LSH:
/* Gotta have special overflow logic here, if we're shifting
* more than MAX_RANGE then just assume we have an invalid
* range.
*/
if (min_val > ilog2(BPF_REGISTER_MAX_RANGE)) {
dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
dst_reg->min_align = 1;
} else {
if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
dst_reg->min_value <<= min_val;
if (!dst_reg->min_align)
dst_reg->min_align = 1;
dst_reg->min_align <<= min_val;
}
if (max_val > ilog2(BPF_REGISTER_MAX_RANGE))
dst_reg->max_value = BPF_REGISTER_MAX_RANGE;
else if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
dst_reg->max_value <<= max_val;
break;
case BPF_RSH:
/* RSH by a negative number is undefined, and the BPF_RSH is an
* unsigned shift, so make the appropriate casts.
*/
if (min_val < 0 || dst_reg->min_value < 0) {
dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
} else {
dst_reg->min_value =
(u64)(dst_reg->min_value) >> min_val;
}
if (min_val < 0) {
dst_reg->min_align = 1;
} else {
dst_reg->min_align >>= (u64) min_val;
if (!dst_reg->min_align)
dst_reg->min_align = 1;
}
if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
dst_reg->max_value >>= max_val;
break;
default:
reset_reg_range_values(regs, insn->dst_reg);
break;
}
check_reg_overflow(dst_reg);
}
/* check validity of 32-bit and 64-bit arithmetic operations */
static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg;
u8 opcode = BPF_OP(insn->code);
int err;
if (opcode == BPF_END || opcode == BPF_NEG) {
if (opcode == BPF_NEG) {
if (BPF_SRC(insn->code) != 0 ||
insn->src_reg != BPF_REG_0 ||
insn->off != 0 || insn->imm != 0) {
verbose("BPF_NEG uses reserved fields\n");
return -EINVAL;
}
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
(insn->imm != 16 && insn->imm != 32 && insn->imm != 64)) {
verbose("BPF_END uses reserved fields\n");
return -EINVAL;
}
}
/* check src operand */
err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->dst_reg)) {
verbose("R%d pointer arithmetic prohibited\n",
insn->dst_reg);
return -EACCES;
}
/* check dest operand */
err = check_reg_arg(regs, insn->dst_reg, DST_OP);
if (err)
return err;
} else if (opcode == BPF_MOV) {
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0 || insn->off != 0) {
verbose("BPF_MOV uses reserved fields\n");
return -EINVAL;
}
/* check src operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
return err;
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
verbose("BPF_MOV uses reserved fields\n");
return -EINVAL;
}
}
/* check dest operand */
err = check_reg_arg(regs, insn->dst_reg, DST_OP);
if (err)
return err;
/* we are setting our register to something new, we need to
* reset its range values.
*/
reset_reg_range_values(regs, insn->dst_reg);
if (BPF_SRC(insn->code) == BPF_X) {
if (BPF_CLASS(insn->code) == BPF_ALU64) {
/* case: R1 = R2
* copy register state to dest reg
*/
regs[insn->dst_reg] = regs[insn->src_reg];
} else {
if (is_pointer_value(env, insn->src_reg)) {
verbose("R%d partial copy of pointer\n",
insn->src_reg);
return -EACCES;
}
mark_reg_unknown_value(regs, insn->dst_reg);
}
} else {
/* case: R = imm
* remember the value we stored into this reg
*/
regs[insn->dst_reg].type = CONST_IMM;
regs[insn->dst_reg].imm = insn->imm;
regs[insn->dst_reg].id = 0;
regs[insn->dst_reg].max_value = insn->imm;
regs[insn->dst_reg].min_value = insn->imm;
regs[insn->dst_reg].min_align = calc_align(insn->imm);
regs[insn->dst_reg].value_from_signed = false;
}
} else if (opcode > BPF_END) {
verbose("invalid BPF_ALU opcode %x\n", opcode);
return -EINVAL;
} else { /* all other ALU ops: and, sub, xor, add, ... */
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0 || insn->off != 0) {
verbose("BPF_ALU uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
return err;
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
verbose("BPF_ALU uses reserved fields\n");
return -EINVAL;
}
}
/* check src2 operand */
err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
if (err)
return err;
if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
verbose("div by zero\n");
return -EINVAL;
}
if ((opcode == BPF_LSH || opcode == BPF_RSH ||
opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
if (insn->imm < 0 || insn->imm >= size) {
verbose("invalid shift %d\n", insn->imm);
return -EINVAL;
}
}
/* check dest operand */
err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
if (err)
return err;
dst_reg = &regs[insn->dst_reg];
/* first we want to adjust our ranges. */
adjust_reg_min_max_vals(env, insn);
/* pattern match 'bpf_add Rx, imm' instruction */
if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 &&
dst_reg->type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) {
dst_reg->type = PTR_TO_STACK;
dst_reg->imm = insn->imm;
return 0;
} else if (opcode == BPF_ADD &&
BPF_CLASS(insn->code) == BPF_ALU64 &&
dst_reg->type == PTR_TO_STACK &&
((BPF_SRC(insn->code) == BPF_X &&
regs[insn->src_reg].type == CONST_IMM) ||
BPF_SRC(insn->code) == BPF_K)) {
if (BPF_SRC(insn->code) == BPF_X)
dst_reg->imm += regs[insn->src_reg].imm;
else
dst_reg->imm += insn->imm;
return 0;
} else if (opcode == BPF_ADD &&
BPF_CLASS(insn->code) == BPF_ALU64 &&
(dst_reg->type == PTR_TO_PACKET ||
(BPF_SRC(insn->code) == BPF_X &&
regs[insn->src_reg].type == PTR_TO_PACKET))) {
/* ptr_to_packet += K|X */
return check_packet_ptr_add(env, insn);
} else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
dst_reg->type == UNKNOWN_VALUE &&
env->allow_ptr_leaks) {
/* unknown += K|X */
return evaluate_reg_alu(env, insn);
} else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
dst_reg->type == CONST_IMM &&
env->allow_ptr_leaks) {
/* reg_imm += K|X */
return evaluate_reg_imm_alu(env, insn);
} else if (is_pointer_value(env, insn->dst_reg)) {
verbose("R%d pointer arithmetic prohibited\n",
insn->dst_reg);
return -EACCES;
} else if (BPF_SRC(insn->code) == BPF_X &&
is_pointer_value(env, insn->src_reg)) {
verbose("R%d pointer arithmetic prohibited\n",
insn->src_reg);
return -EACCES;
}
/* If we did pointer math on a map value then just set it to our
* PTR_TO_MAP_VALUE_ADJ type so we can deal with any stores or
* loads to this register appropriately, otherwise just mark the
* register as unknown.
*/
if (env->allow_ptr_leaks &&
BPF_CLASS(insn->code) == BPF_ALU64 && opcode == BPF_ADD &&
(dst_reg->type == PTR_TO_MAP_VALUE ||
dst_reg->type == PTR_TO_MAP_VALUE_ADJ))
dst_reg->type = PTR_TO_MAP_VALUE_ADJ;
else
mark_reg_unknown_value(regs, insn->dst_reg);
}
return 0;
}
static void find_good_pkt_pointers(struct bpf_verifier_state *state,
struct bpf_reg_state *dst_reg)
{
struct bpf_reg_state *regs = state->regs, *reg;
int i;
/* LLVM can generate two kind of checks:
*
* Type 1:
*
* r2 = r3;
* r2 += 8;
* if (r2 > pkt_end) goto <handle exception>
* <access okay>
*
* Where:
* r2 == dst_reg, pkt_end == src_reg
* r2=pkt(id=n,off=8,r=0)
* r3=pkt(id=n,off=0,r=0)
*
* Type 2:
*
* r2 = r3;
* r2 += 8;
* if (pkt_end >= r2) goto <access okay>
* <handle exception>
*
* Where:
* pkt_end == dst_reg, r2 == src_reg
* r2=pkt(id=n,off=8,r=0)
* r3=pkt(id=n,off=0,r=0)
*
* Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
* so that range of bytes [r3, r3 + 8) is safe to access.
*/
for (i = 0; i < MAX_BPF_REG; i++)
if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id)
/* keep the maximum range already checked */
regs[i].range = max(regs[i].range, dst_reg->off);
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] != STACK_SPILL)
continue;
reg = &state->spilled_regs[i / BPF_REG_SIZE];
if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id)
reg->range = max(reg->range, dst_reg->off);
}
}
/* Adjusts the register min/max values in the case that the dst_reg is the
* variable register that we are working on, and src_reg is a constant or we're
* simply doing a BPF_K check.
*/
static void reg_set_min_max(struct bpf_reg_state *true_reg,
struct bpf_reg_state *false_reg, u64 val,
u8 opcode)
{
bool value_from_signed = true;
bool is_range = true;
switch (opcode) {
case BPF_JEQ:
/* If this is false then we know nothing Jon Snow, but if it is
* true then we know for sure.
*/
true_reg->max_value = true_reg->min_value = val;
is_range = false;
break;
case BPF_JNE:
/* If this is true we know nothing Jon Snow, but if it is false
* we know the value for sure;
*/
false_reg->max_value = false_reg->min_value = val;
is_range = false;
break;
case BPF_JGT:
value_from_signed = false;
/* fallthrough */
case BPF_JSGT:
if (true_reg->value_from_signed != value_from_signed)
reset_reg_range_values(true_reg, 0);
if (false_reg->value_from_signed != value_from_signed)
reset_reg_range_values(false_reg, 0);
if (opcode == BPF_JGT) {
/* Unsigned comparison, the minimum value is 0. */
false_reg->min_value = 0;
}
/* If this is false then we know the maximum val is val,
* otherwise we know the min val is val+1.
*/
false_reg->max_value = val;
false_reg->value_from_signed = value_from_signed;
true_reg->min_value = val + 1;
true_reg->value_from_signed = value_from_signed;
break;
case BPF_JGE:
value_from_signed = false;
/* fallthrough */
case BPF_JSGE:
if (true_reg->value_from_signed != value_from_signed)
reset_reg_range_values(true_reg, 0);
if (false_reg->value_from_signed != value_from_signed)
reset_reg_range_values(false_reg, 0);
if (opcode == BPF_JGE) {
/* Unsigned comparison, the minimum value is 0. */
false_reg->min_value = 0;
}
/* If this is false then we know the maximum value is val - 1,
* otherwise we know the mimimum value is val.
*/
false_reg->max_value = val - 1;
false_reg->value_from_signed = value_from_signed;
true_reg->min_value = val;
true_reg->value_from_signed = value_from_signed;
break;
default:
break;
}
check_reg_overflow(false_reg);
check_reg_overflow(true_reg);
if (is_range) {
if (__is_pointer_value(false, false_reg))
reset_reg_range_values(false_reg, 0);
if (__is_pointer_value(false, true_reg))
reset_reg_range_values(true_reg, 0);
}
}
/* Same as above, but for the case that dst_reg is a CONST_IMM reg and src_reg
* is the variable reg.
*/
static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
struct bpf_reg_state *false_reg, u64 val,
u8 opcode)
{
bool value_from_signed = true;
bool is_range = true;
switch (opcode) {
case BPF_JEQ:
/* If this is false then we know nothing Jon Snow, but if it is
* true then we know for sure.
*/
true_reg->max_value = true_reg->min_value = val;
is_range = false;
break;
case BPF_JNE:
/* If this is true we know nothing Jon Snow, but if it is false
* we know the value for sure;
*/
false_reg->max_value = false_reg->min_value = val;
is_range = false;
break;
case BPF_JGT:
value_from_signed = false;
/* fallthrough */
case BPF_JSGT:
if (true_reg->value_from_signed != value_from_signed)
reset_reg_range_values(true_reg, 0);
if (false_reg->value_from_signed != value_from_signed)
reset_reg_range_values(false_reg, 0);
if (opcode == BPF_JGT) {
/* Unsigned comparison, the minimum value is 0. */
true_reg->min_value = 0;
}
/*
* If this is false, then the val is <= the register, if it is
* true the register <= to the val.
*/
false_reg->min_value = val;
false_reg->value_from_signed = value_from_signed;
true_reg->max_value = val - 1;
true_reg->value_from_signed = value_from_signed;
break;
case BPF_JGE:
value_from_signed = false;
/* fallthrough */
case BPF_JSGE:
if (true_reg->value_from_signed != value_from_signed)
reset_reg_range_values(true_reg, 0);
if (false_reg->value_from_signed != value_from_signed)
reset_reg_range_values(false_reg, 0);
if (opcode == BPF_JGE) {
/* Unsigned comparison, the minimum value is 0. */
true_reg->min_value = 0;
}
/* If this is false then constant < register, if it is true then
* the register < constant.
*/
false_reg->min_value = val + 1;
false_reg->value_from_signed = value_from_signed;
true_reg->max_value = val;
true_reg->value_from_signed = value_from_signed;
break;
default:
break;
}
check_reg_overflow(false_reg);
check_reg_overflow(true_reg);
if (is_range) {
if (__is_pointer_value(false, false_reg))
reset_reg_range_values(false_reg, 0);
if (__is_pointer_value(false, true_reg))
reset_reg_range_values(true_reg, 0);
}
}
static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id,
enum bpf_reg_type type)
{
struct bpf_reg_state *reg = &regs[regno];
if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) {
if (type == UNKNOWN_VALUE) {
__mark_reg_unknown_value(regs, regno);
} else if (reg->map_ptr->inner_map_meta) {
reg->type = CONST_PTR_TO_MAP;
reg->map_ptr = reg->map_ptr->inner_map_meta;
} else {
reg->type = type;
}
/* We don't need id from this point onwards anymore, thus we
* should better reset it, so that state pruning has chances
* to take effect.
*/
reg->id = 0;
}
}
/* The logic is similar to find_good_pkt_pointers(), both could eventually
* be folded together at some point.
*/
static void mark_map_regs(struct bpf_verifier_state *state, u32 regno,
enum bpf_reg_type type)
{
struct bpf_reg_state *regs = state->regs;
u32 id = regs[regno].id;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
mark_map_reg(regs, i, id, type);
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] != STACK_SPILL)
continue;
mark_map_reg(state->spilled_regs, i / BPF_REG_SIZE, id, type);
}
}
static int check_cond_jmp_op(struct bpf_verifier_env *env,
struct bpf_insn *insn, int *insn_idx)
{
struct bpf_verifier_state *other_branch, *this_branch = &env->cur_state;
struct bpf_reg_state *regs = this_branch->regs, *dst_reg;
u8 opcode = BPF_OP(insn->code);
int err;
if (opcode > BPF_EXIT) {
verbose("invalid BPF_JMP opcode %x\n", opcode);
return -EINVAL;
}
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0) {
verbose("BPF_JMP uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->src_reg)) {
verbose("R%d pointer comparison prohibited\n",
insn->src_reg);
return -EACCES;
}
} else {
if (insn->src_reg != BPF_REG_0) {
verbose("BPF_JMP uses reserved fields\n");
return -EINVAL;
}
}
/* check src2 operand */
err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
if (err)
return err;
dst_reg = &regs[insn->dst_reg];
/* detect if R == 0 where R was initialized to zero earlier */
if (BPF_SRC(insn->code) == BPF_K &&
(opcode == BPF_JEQ || opcode == BPF_JNE) &&
dst_reg->type == CONST_IMM && dst_reg->imm == insn->imm) {
if (opcode == BPF_JEQ) {
/* if (imm == imm) goto pc+off;
* only follow the goto, ignore fall-through
*/
*insn_idx += insn->off;
return 0;
} else {
/* if (imm != imm) goto pc+off;
* only follow fall-through branch, since
* that's where the program will go
*/
return 0;
}
}
other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
if (!other_branch)
return -EFAULT;
/* detect if we are comparing against a constant value so we can adjust
* our min/max values for our dst register.
*/
if (BPF_SRC(insn->code) == BPF_X) {
if (regs[insn->src_reg].type == CONST_IMM)
reg_set_min_max(&other_branch->regs[insn->dst_reg],
dst_reg, regs[insn->src_reg].imm,
opcode);
else if (dst_reg->type == CONST_IMM)
reg_set_min_max_inv(&other_branch->regs[insn->src_reg],
&regs[insn->src_reg], dst_reg->imm,
opcode);
} else {
reg_set_min_max(&other_branch->regs[insn->dst_reg],
dst_reg, insn->imm, opcode);
}
/* detect if R == 0 where R is returned from bpf_map_lookup_elem() */
if (BPF_SRC(insn->code) == BPF_K &&
insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
/* Mark all identical map registers in each branch as either
* safe or unknown depending R == 0 or R != 0 conditional.
*/
mark_map_regs(this_branch, insn->dst_reg,
opcode == BPF_JEQ ? PTR_TO_MAP_VALUE : UNKNOWN_VALUE);
mark_map_regs(other_branch, insn->dst_reg,
opcode == BPF_JEQ ? UNKNOWN_VALUE : PTR_TO_MAP_VALUE);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
dst_reg->type == PTR_TO_PACKET &&
regs[insn->src_reg].type == PTR_TO_PACKET_END) {
find_good_pkt_pointers(this_branch, dst_reg);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE &&
dst_reg->type == PTR_TO_PACKET_END &&
regs[insn->src_reg].type == PTR_TO_PACKET) {
find_good_pkt_pointers(other_branch, &regs[insn->src_reg]);
} else if (is_pointer_value(env, insn->dst_reg)) {
verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
return -EACCES;
}
if (log_level)
print_verifier_state(this_branch);
return 0;
}
/* return the map pointer stored inside BPF_LD_IMM64 instruction */
static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
{
u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
return (struct bpf_map *) (unsigned long) imm64;
}
/* verify BPF_LD_IMM64 instruction */
static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
int err;
if (BPF_SIZE(insn->code) != BPF_DW) {
verbose("invalid BPF_LD_IMM insn\n");
return -EINVAL;
}
if (insn->off != 0) {
verbose("BPF_LD_IMM64 uses reserved fields\n");
return -EINVAL;
}
err = check_reg_arg(regs, insn->dst_reg, DST_OP);
if (err)
return err;
if (insn->src_reg == 0) {
u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
regs[insn->dst_reg].type = CONST_IMM;
regs[insn->dst_reg].imm = imm;
regs[insn->dst_reg].id = 0;
return 0;
}
/* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
return 0;
}
static bool may_access_skb(enum bpf_prog_type type)
{
switch (type) {
case BPF_PROG_TYPE_SOCKET_FILTER:
case BPF_PROG_TYPE_SCHED_CLS:
case BPF_PROG_TYPE_SCHED_ACT:
return true;
default:
return false;
}
}
/* verify safety of LD_ABS|LD_IND instructions:
* - they can only appear in the programs where ctx == skb
* - since they are wrappers of function calls, they scratch R1-R5 registers,
* preserve R6-R9, and store return value into R0
*
* Implicit input:
* ctx == skb == R6 == CTX
*
* Explicit input:
* SRC == any register
* IMM == 32-bit immediate
*
* Output:
* R0 - 8/16/32-bit skb data converted to cpu endianness
*/
static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
u8 mode = BPF_MODE(insn->code);
int i, err;
if (!may_access_skb(env->prog->type)) {
verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
return -EINVAL;
}
if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
BPF_SIZE(insn->code) == BPF_DW ||
(mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
verbose("BPF_LD_[ABS|IND] uses reserved fields\n");
return -EINVAL;
}
/* check whether implicit source operand (register R6) is readable */
err = check_reg_arg(regs, BPF_REG_6, SRC_OP);
if (err)
return err;
if (regs[BPF_REG_6].type != PTR_TO_CTX) {
verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
return -EINVAL;
}
if (mode == BPF_IND) {
/* check explicit source operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
return err;
}
/* reset caller saved regs to unreadable */
for (i = 0; i < CALLER_SAVED_REGS; i++)
mark_reg_not_init(regs, caller_saved[i]);
/* mark destination R0 register as readable, since it contains
* the value fetched from the packet
*/
regs[BPF_REG_0].type = UNKNOWN_VALUE;
return 0;
}
/* non-recursive DFS pseudo code
* 1 procedure DFS-iterative(G,v):
* 2 label v as discovered
* 3 let S be a stack
* 4 S.push(v)
* 5 while S is not empty
* 6 t <- S.pop()
* 7 if t is what we're looking for:
* 8 return t
* 9 for all edges e in G.adjacentEdges(t) do
* 10 if edge e is already labelled
* 11 continue with the next edge
* 12 w <- G.adjacentVertex(t,e)
* 13 if vertex w is not discovered and not explored
* 14 label e as tree-edge
* 15 label w as discovered
* 16 S.push(w)
* 17 continue at 5
* 18 else if vertex w is discovered
* 19 label e as back-edge
* 20 else
* 21 // vertex w is explored
* 22 label e as forward- or cross-edge
* 23 label t as explored
* 24 S.pop()
*
* convention:
* 0x10 - discovered
* 0x11 - discovered and fall-through edge labelled
* 0x12 - discovered and fall-through and branch edges labelled
* 0x20 - explored
*/
enum {
DISCOVERED = 0x10,
EXPLORED = 0x20,
FALLTHROUGH = 1,
BRANCH = 2,
};
#define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L)
static int *insn_stack; /* stack of insns to process */
static int cur_stack; /* current stack index */
static int *insn_state;
/* t, w, e - match pseudo-code above:
* t - index of current instruction
* w - next instruction
* e - edge
*/
static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
{
if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
return 0;
if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
return 0;
if (w < 0 || w >= env->prog->len) {
verbose("jump out of range from insn %d to %d\n", t, w);
return -EINVAL;
}
if (e == BRANCH)
/* mark branch target for state pruning */
env->explored_states[w] = STATE_LIST_MARK;
if (insn_state[w] == 0) {
/* tree-edge */
insn_state[t] = DISCOVERED | e;
insn_state[w] = DISCOVERED;
if (cur_stack >= env->prog->len)
return -E2BIG;
insn_stack[cur_stack++] = w;
return 1;
} else if ((insn_state[w] & 0xF0) == DISCOVERED) {
verbose("back-edge from insn %d to %d\n", t, w);
return -EINVAL;
} else if (insn_state[w] == EXPLORED) {
/* forward- or cross-edge */
insn_state[t] = DISCOVERED | e;
} else {
verbose("insn state internal bug\n");
return -EFAULT;
}
return 0;
}
/* non-recursive depth-first-search to detect loops in BPF program
* loop == back-edge in directed graph
*/
static int check_cfg(struct bpf_verifier_env *env)
{
struct bpf_insn *insns = env->prog->insnsi;
int insn_cnt = env->prog->len;
int ret = 0;
int i, t;
insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
if (!insn_state)
return -ENOMEM;
insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
if (!insn_stack) {
kfree(insn_state);
return -ENOMEM;
}
insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
insn_stack[0] = 0; /* 0 is the first instruction */
cur_stack = 1;
peek_stack:
if (cur_stack == 0)
goto check_state;
t = insn_stack[cur_stack - 1];
if (BPF_CLASS(insns[t].code) == BPF_JMP) {
u8 opcode = BPF_OP(insns[t].code);
if (opcode == BPF_EXIT) {
goto mark_explored;
} else if (opcode == BPF_CALL) {
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
if (t + 1 < insn_cnt)
env->explored_states[t + 1] = STATE_LIST_MARK;
} else if (opcode == BPF_JA) {
if (BPF_SRC(insns[t].code) != BPF_K) {
ret = -EINVAL;
goto err_free;
}
/* unconditional jump with single edge */
ret = push_insn(t, t + insns[t].off + 1,
FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
/* tell verifier to check for equivalent states
* after every call and jump
*/
if (t + 1 < insn_cnt)
env->explored_states[t + 1] = STATE_LIST_MARK;
} else {
/* conditional jump with two edges */
env->explored_states[t] = STATE_LIST_MARK;
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
}
} else {
/* all other non-branch instructions with single
* fall-through edge
*/
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
}
mark_explored:
insn_state[t] = EXPLORED;
if (cur_stack-- <= 0) {
verbose("pop stack internal bug\n");
ret = -EFAULT;
goto err_free;
}
goto peek_stack;
check_state:
for (i = 0; i < insn_cnt; i++) {
if (insn_state[i] != EXPLORED) {
verbose("unreachable insn %d\n", i);
ret = -EINVAL;
goto err_free;
}
}
ret = 0; /* cfg looks good */
err_free:
kfree(insn_state);
kfree(insn_stack);
return ret;
}
/* the following conditions reduce the number of explored insns
* from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet
*/
static bool compare_ptrs_to_packet(struct bpf_verifier_env *env,
struct bpf_reg_state *old,
struct bpf_reg_state *cur)
{
if (old->id != cur->id)
return false;
/* old ptr_to_packet is more conservative, since it allows smaller
* range. Ex:
* old(off=0,r=10) is equal to cur(off=0,r=20), because
* old(off=0,r=10) means that with range=10 the verifier proceeded
* further and found no issues with the program. Now we're in the same
* spot with cur(off=0,r=20), so we're safe too, since anything further
* will only be looking at most 10 bytes after this pointer.
*/
if (old->off == cur->off && old->range < cur->range)
return true;
/* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0)
* since both cannot be used for packet access and safe(old)
* pointer has smaller off that could be used for further
* 'if (ptr > data_end)' check
* Ex:
* old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean
* that we cannot access the packet.
* The safe range is:
* [ptr, ptr + range - off)
* so whenever off >=range, it means no safe bytes from this pointer.
* When comparing old->off <= cur->off, it means that older code
* went with smaller offset and that offset was later
* used to figure out the safe range after 'if (ptr > data_end)' check
* Say, 'old' state was explored like:
* ... R3(off=0, r=0)
* R4 = R3 + 20
* ... now R4(off=20,r=0) <-- here
* if (R4 > data_end)
* ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access.
* ... the code further went all the way to bpf_exit.
* Now the 'cur' state at the mark 'here' has R4(off=30,r=0).
* old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier
* goes further, such cur_R4 will give larger safe packet range after
* 'if (R4 > data_end)' and all further insn were already good with r=20,
* so they will be good with r=30 and we can prune the search.
*/
if (!env->strict_alignment && old->off <= cur->off &&
old->off >= old->range && cur->off >= cur->range)
return true;
return false;
}
/* compare two verifier states
*
* all states stored in state_list are known to be valid, since
* verifier reached 'bpf_exit' instruction through them
*
* this function is called when verifier exploring different branches of
* execution popped from the state stack. If it sees an old state that has
* more strict register state and more strict stack state then this execution
* branch doesn't need to be explored further, since verifier already
* concluded that more strict state leads to valid finish.
*
* Therefore two states are equivalent if register state is more conservative
* and explored stack state is more conservative than the current one.
* Example:
* explored current
* (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
* (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
*
* In other words if current stack state (one being explored) has more
* valid slots than old one that already passed validation, it means
* the verifier can stop exploring and conclude that current state is valid too
*
* Similarly with registers. If explored state has register type as invalid
* whereas register type in current state is meaningful, it means that
* the current state will reach 'bpf_exit' instruction safely
*/
static bool states_equal(struct bpf_verifier_env *env,
struct bpf_verifier_state *old,
struct bpf_verifier_state *cur)
{
bool varlen_map_access = env->varlen_map_value_access;
struct bpf_reg_state *rold, *rcur;
int i;
for (i = 0; i < MAX_BPF_REG; i++) {
rold = &old->regs[i];
rcur = &cur->regs[i];
if (memcmp(rold, rcur, sizeof(*rold)) == 0)
continue;
/* If the ranges were not the same, but everything else was and
* we didn't do a variable access into a map then we are a-ok.
*/
if (!varlen_map_access &&
memcmp(rold, rcur, offsetofend(struct bpf_reg_state, id)) == 0)
continue;
/* If we didn't map access then again we don't care about the
* mismatched range values and it's ok if our old type was
* UNKNOWN and we didn't go to a NOT_INIT'ed reg.
*/
if (rold->type == NOT_INIT ||
(!varlen_map_access && rold->type == UNKNOWN_VALUE &&
rcur->type != NOT_INIT))
continue;
/* Don't care about the reg->id in this case. */
if (rold->type == PTR_TO_MAP_VALUE_OR_NULL &&
rcur->type == PTR_TO_MAP_VALUE_OR_NULL &&
rold->map_ptr == rcur->map_ptr)
continue;
if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET &&
compare_ptrs_to_packet(env, rold, rcur))
continue;
return false;
}
for (i = 0; i < MAX_BPF_STACK; i++) {
if (old->stack_slot_type[i] == STACK_INVALID)
continue;
if (old->stack_slot_type[i] != cur->stack_slot_type[i])
/* Ex: old explored (safe) state has STACK_SPILL in
* this stack slot, but current has has STACK_MISC ->
* this verifier states are not equivalent,
* return false to continue verification of this path
*/
return false;
if (i % BPF_REG_SIZE)
continue;
if (old->stack_slot_type[i] != STACK_SPILL)
continue;
if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
&cur->spilled_regs[i / BPF_REG_SIZE],
sizeof(old->spilled_regs[0])))
/* when explored and current stack slot types are
* the same, check that stored pointers types
* are the same as well.
* Ex: explored safe path could have stored
* (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -8}
* but current path has stored:
* (bpf_reg_state) {.type = PTR_TO_STACK, .imm = -16}
* such verifier states are not equivalent.
* return false to continue verification of this path
*/
return false;
else
continue;
}
return true;
}
static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
{
struct bpf_verifier_state_list *new_sl;
struct bpf_verifier_state_list *sl;
sl = env->explored_states[insn_idx];
if (!sl)
/* this 'insn_idx' instruction wasn't marked, so we will not
* be doing state search here
*/
return 0;
while (sl != STATE_LIST_MARK) {
if (states_equal(env, &sl->state, &env->cur_state))
/* reached equivalent register/stack state,
* prune the search
*/
return 1;
sl = sl->next;
}
/* there were no equivalent states, remember current one.
* technically the current state is not proven to be safe yet,
* but it will either reach bpf_exit (which means it's safe) or
* it will be rejected. Since there are no loops, we won't be
* seeing this 'insn_idx' instruction again on the way to bpf_exit
*/
new_sl = kmalloc(sizeof(struct bpf_verifier_state_list), GFP_USER);
if (!new_sl)
return -ENOMEM;
/* add new state to the head of linked list */
memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
new_sl->next = env->explored_states[insn_idx];
env->explored_states[insn_idx] = new_sl;
return 0;
}
static int ext_analyzer_insn_hook(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx)
{
if (!env->analyzer_ops || !env->analyzer_ops->insn_hook)
return 0;
return env->analyzer_ops->insn_hook(env, insn_idx, prev_insn_idx);
}
static int do_check(struct bpf_verifier_env *env)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_insn *insns = env->prog->insnsi;
struct bpf_reg_state *regs = state->regs;
int insn_cnt = env->prog->len;
int insn_idx, prev_insn_idx = 0;
int insn_processed = 0;
bool do_print_state = false;
init_reg_state(regs);
insn_idx = 0;
env->varlen_map_value_access = false;
for (;;) {
struct bpf_insn *insn;
u8 class;
int err;
if (insn_idx >= insn_cnt) {
verbose("invalid insn idx %d insn_cnt %d\n",
insn_idx, insn_cnt);
return -EFAULT;
}
insn = &insns[insn_idx];
class = BPF_CLASS(insn->code);
if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
verbose("BPF program is too large. Processed %d insn\n",
insn_processed);
return -E2BIG;
}
err = is_state_visited(env, insn_idx);
if (err < 0)
return err;
if (err == 1) {
/* found equivalent state, can prune the search */
if (log_level) {
if (do_print_state)
verbose("\nfrom %d to %d: safe\n",
prev_insn_idx, insn_idx);
else
verbose("%d: safe\n", insn_idx);
}
goto process_bpf_exit;
}
if (need_resched())
cond_resched();
if (log_level > 1 || (log_level && do_print_state)) {
if (log_level > 1)
verbose("%d:", insn_idx);
else
verbose("\nfrom %d to %d:",
prev_insn_idx, insn_idx);
print_verifier_state(&env->cur_state);
do_print_state = false;
}
if (log_level) {
verbose("%d: ", insn_idx);
print_bpf_insn(env, insn);
}
err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx);
if (err)
return err;
if (class == BPF_ALU || class == BPF_ALU64) {
err = check_alu_op(env, insn);
if (err)
return err;
} else if (class == BPF_LDX) {
enum bpf_reg_type *prev_src_type, src_reg_type;
/* check for reserved fields is already done */
/* check src operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
return err;
err = check_reg_arg(regs, insn->dst_reg, DST_OP_NO_MARK);
if (err)
return err;
src_reg_type = regs[insn->src_reg].type;
/* check that memory (src_reg + off) is readable,
* the state of dst_reg will be updated by this func
*/
err = check_mem_access(env, insn_idx, insn->src_reg, insn->off,
BPF_SIZE(insn->code), BPF_READ,
insn->dst_reg);
if (err)
return err;
prev_src_type = &env->insn_aux_data[insn_idx].ptr_type;
if (*prev_src_type == NOT_INIT) {
/* saw a valid insn
* dst_reg = *(u32 *)(src_reg + off)
* save type to validate intersecting paths
*/
*prev_src_type = src_reg_type;
} else if (src_reg_type != *prev_src_type &&
(src_reg_type == PTR_TO_CTX ||
*prev_src_type == PTR_TO_CTX)) {
/* ABuser program is trying to use the same insn
* dst_reg = *(u32*) (src_reg + off)
* with different pointer types:
* src_reg == ctx in one branch and
* src_reg == stack|map in some other branch.
* Reject it.
*/
verbose("same insn cannot be used with different pointers\n");
return -EINVAL;
}
} else if (class == BPF_STX) {
enum bpf_reg_type *prev_dst_type, dst_reg_type;
if (BPF_MODE(insn->code) == BPF_XADD) {
err = check_xadd(env, insn_idx, insn);
if (err)
return err;
insn_idx++;
continue;
}
/* check src1 operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
return err;
/* check src2 operand */
err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
if (err)
return err;
dst_reg_type = regs[insn->dst_reg].type;
/* check that memory (dst_reg + off) is writeable */
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_WRITE,
insn->src_reg);
if (err)
return err;
prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type;
if (*prev_dst_type == NOT_INIT) {
*prev_dst_type = dst_reg_type;
} else if (dst_reg_type != *prev_dst_type &&
(dst_reg_type == PTR_TO_CTX ||
*prev_dst_type == PTR_TO_CTX)) {
verbose("same insn cannot be used with different pointers\n");
return -EINVAL;
}
} else if (class == BPF_ST) {
if (BPF_MODE(insn->code) != BPF_MEM ||
insn->src_reg != BPF_REG_0) {
verbose("BPF_ST uses reserved fields\n");
return -EINVAL;
}
/* check src operand */
err = check_reg_arg(regs, insn->dst_reg, SRC_OP);
if (err)
return err;
/* check that memory (dst_reg + off) is writeable */
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_WRITE,
-1);
if (err)
return err;
} else if (class == BPF_JMP) {
u8 opcode = BPF_OP(insn->code);
if (opcode == BPF_CALL) {
if (BPF_SRC(insn->code) != BPF_K ||
insn->off != 0 ||
insn->src_reg != BPF_REG_0 ||
insn->dst_reg != BPF_REG_0) {
verbose("BPF_CALL uses reserved fields\n");
return -EINVAL;
}
err = check_call(env, insn->imm, insn_idx);
if (err)
return err;
} else if (opcode == BPF_JA) {
if (BPF_SRC(insn->code) != BPF_K ||
insn->imm != 0 ||
insn->src_reg != BPF_REG_0 ||
insn->dst_reg != BPF_REG_0) {
verbose("BPF_JA uses reserved fields\n");
return -EINVAL;
}
insn_idx += insn->off + 1;
continue;
} else if (opcode == BPF_EXIT) {
if (BPF_SRC(insn->code) != BPF_K ||
insn->imm != 0 ||
insn->src_reg != BPF_REG_0 ||
insn->dst_reg != BPF_REG_0) {
verbose("BPF_EXIT uses reserved fields\n");
return -EINVAL;
}
/* eBPF calling convetion is such that R0 is used
* to return the value from eBPF program.
* Make sure that it's readable at this time
* of bpf_exit, which means that program wrote
* something into it earlier
*/
err = check_reg_arg(regs, BPF_REG_0, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, BPF_REG_0)) {
verbose("R0 leaks addr as return value\n");
return -EACCES;
}
process_bpf_exit:
insn_idx = pop_stack(env, &prev_insn_idx);
if (insn_idx < 0) {
break;
} else {
do_print_state = true;
continue;
}
} else {
err = check_cond_jmp_op(env, insn, &insn_idx);
if (err)
return err;
}
} else if (class == BPF_LD) {
u8 mode = BPF_MODE(insn->code);
if (mode == BPF_ABS || mode == BPF_IND) {
err = check_ld_abs(env, insn);
if (err)
return err;
} else if (mode == BPF_IMM) {
err = check_ld_imm(env, insn);
if (err)
return err;
insn_idx++;
} else {
verbose("invalid BPF_LD mode\n");
return -EINVAL;
}
reset_reg_range_values(regs, insn->dst_reg);
} else {
verbose("unknown insn class %d\n", class);
return -EINVAL;
}
insn_idx++;
}
verbose("processed %d insns, stack depth %d\n",
insn_processed, env->prog->aux->stack_depth);
return 0;
}
static int check_map_prealloc(struct bpf_map *map)
{
return (map->map_type != BPF_MAP_TYPE_HASH &&
map->map_type != BPF_MAP_TYPE_PERCPU_HASH &&
map->map_type != BPF_MAP_TYPE_HASH_OF_MAPS) ||
!(map->map_flags & BPF_F_NO_PREALLOC);
}
static int check_map_prog_compatibility(struct bpf_map *map,
struct bpf_prog *prog)
{
/* Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use
* preallocated hash maps, since doing memory allocation
* in overflow_handler can crash depending on where nmi got
* triggered.
*/
if (prog->type == BPF_PROG_TYPE_PERF_EVENT) {
if (!check_map_prealloc(map)) {
verbose("perf_event programs can only use preallocated hash map\n");
return -EINVAL;
}
if (map->inner_map_meta &&
!check_map_prealloc(map->inner_map_meta)) {
verbose("perf_event programs can only use preallocated inner hash map\n");
return -EINVAL;
}
}
return 0;
}
/* look for pseudo eBPF instructions that access map FDs and
* replace them with actual map pointers
*/
static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env)
{
struct bpf_insn *insn = env->prog->insnsi;
int insn_cnt = env->prog->len;
int i, j, err;
err = bpf_prog_calc_tag(env->prog);
if (err)
return err;
for (i = 0; i < insn_cnt; i++, insn++) {
if (BPF_CLASS(insn->code) == BPF_LDX &&
(BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
verbose("BPF_LDX uses reserved fields\n");
return -EINVAL;
}
if (BPF_CLASS(insn->code) == BPF_STX &&
((BPF_MODE(insn->code) != BPF_MEM &&
BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
verbose("BPF_STX uses reserved fields\n");
return -EINVAL;
}
if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
struct bpf_map *map;
struct fd f;
if (i == insn_cnt - 1 || insn[1].code != 0 ||
insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
insn[1].off != 0) {
verbose("invalid bpf_ld_imm64 insn\n");
return -EINVAL;
}
if (insn->src_reg == 0)
/* valid generic load 64-bit imm */
goto next_insn;
if (insn->src_reg != BPF_PSEUDO_MAP_FD) {
verbose("unrecognized bpf_ld_imm64 insn\n");
return -EINVAL;
}
f = fdget(insn->imm);
map = __bpf_map_get(f);
if (IS_ERR(map)) {
verbose("fd %d is not pointing to valid bpf_map\n",
insn->imm);
return PTR_ERR(map);
}
err = check_map_prog_compatibility(map, env->prog);
if (err) {
fdput(f);
return err;
}
/* store map pointer inside BPF_LD_IMM64 instruction */
insn[0].imm = (u32) (unsigned long) map;
insn[1].imm = ((u64) (unsigned long) map) >> 32;
/* check whether we recorded this map already */
for (j = 0; j < env->used_map_cnt; j++)
if (env->used_maps[j] == map) {
fdput(f);
goto next_insn;
}
if (env->used_map_cnt >= MAX_USED_MAPS) {
fdput(f);
return -E2BIG;
}
/* hold the map. If the program is rejected by verifier,
* the map will be released by release_maps() or it
* will be used by the valid program until it's unloaded
* and all maps are released in free_bpf_prog_info()
*/
map = bpf_map_inc(map, false);
if (IS_ERR(map)) {
fdput(f);
return PTR_ERR(map);
}
env->used_maps[env->used_map_cnt++] = map;
fdput(f);
next_insn:
insn++;
i++;
}
}
/* now all pseudo BPF_LD_IMM64 instructions load valid
* 'struct bpf_map *' into a register instead of user map_fd.
* These pointers will be used later by verifier to validate map access.
*/
return 0;
}
/* drop refcnt of maps used by the rejected program */
static void release_maps(struct bpf_verifier_env *env)
{
int i;
for (i = 0; i < env->used_map_cnt; i++)
bpf_map_put(env->used_maps[i]);
}
/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env)
{
struct bpf_insn *insn = env->prog->insnsi;
int insn_cnt = env->prog->len;
int i;
for (i = 0; i < insn_cnt; i++, insn++)
if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
insn->src_reg = 0;
}
/* single env->prog->insni[off] instruction was replaced with the range
* insni[off, off + cnt). Adjust corresponding insn_aux_data by copying
* [0, off) and [off, end) to new locations, so the patched range stays zero
*/
static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len,
u32 off, u32 cnt)
{
struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
if (cnt == 1)
return 0;
new_data = vzalloc(sizeof(struct bpf_insn_aux_data) * prog_len);
if (!new_data)
return -ENOMEM;
memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off);
memcpy(new_data + off + cnt - 1, old_data + off,
sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1));
env->insn_aux_data = new_data;
vfree(old_data);
return 0;
}
static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off,
const struct bpf_insn *patch, u32 len)
{
struct bpf_prog *new_prog;
new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
if (!new_prog)
return NULL;
if (adjust_insn_aux_data(env, new_prog->len, off, len))
return NULL;
return new_prog;
}
/* convert load instructions that access fields of 'struct __sk_buff'
* into sequence of instructions that access fields of 'struct sk_buff'
*/
static int convert_ctx_accesses(struct bpf_verifier_env *env)
{
const struct bpf_verifier_ops *ops = env->prog->aux->ops;
int i, cnt, size, ctx_field_size, delta = 0;
const int insn_cnt = env->prog->len;
struct bpf_insn insn_buf[16], *insn;
struct bpf_prog *new_prog;
enum bpf_access_type type;
bool is_narrower_load;
u32 target_size;
if (ops->gen_prologue) {
cnt = ops->gen_prologue(insn_buf, env->seen_direct_write,
env->prog);
if (cnt >= ARRAY_SIZE(insn_buf)) {
verbose("bpf verifier is misconfigured\n");
return -EINVAL;
} else if (cnt) {
new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
env->prog = new_prog;
delta += cnt - 1;
}
}
if (!ops->convert_ctx_access)
return 0;
insn = env->prog->insnsi + delta;
for (i = 0; i < insn_cnt; i++, insn++) {
if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_H) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
type = BPF_READ;
else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) ||
insn->code == (BPF_STX | BPF_MEM | BPF_H) ||
insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
insn->code == (BPF_STX | BPF_MEM | BPF_DW))
type = BPF_WRITE;
else
continue;
if (env->insn_aux_data[i + delta].ptr_type != PTR_TO_CTX)
continue;
ctx_field_size = env->insn_aux_data[i + delta].ctx_field_size;
size = BPF_LDST_BYTES(insn);
/* If the read access is a narrower load of the field,
* convert to a 4/8-byte load, to minimum program type specific
* convert_ctx_access changes. If conversion is successful,
* we will apply proper mask to the result.
*/
is_narrower_load = size < ctx_field_size;
if (is_narrower_load) {
u32 off = insn->off;
u8 size_code;
if (type == BPF_WRITE) {
verbose("bpf verifier narrow ctx access misconfigured\n");
return -EINVAL;
}
size_code = BPF_H;
if (ctx_field_size == 4)
size_code = BPF_W;
else if (ctx_field_size == 8)
size_code = BPF_DW;
insn->off = off & ~(ctx_field_size - 1);
insn->code = BPF_LDX | BPF_MEM | size_code;
}
target_size = 0;
cnt = ops->convert_ctx_access(type, insn, insn_buf, env->prog,
&target_size);
if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf) ||
(ctx_field_size && !target_size)) {
verbose("bpf verifier is misconfigured\n");
return -EINVAL;
}
if (is_narrower_load && size < target_size) {
if (ctx_field_size <= 4)
insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg,
(1 << size * 8) - 1);
else
insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg,
(1 << size * 8) - 1);
}
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
/* keep walking new program and skip insns we just inserted */
env->prog = new_prog;
insn = new_prog->insnsi + i + delta;
}
return 0;
}
/* fixup insn->imm field of bpf_call instructions
* and inline eligible helpers as explicit sequence of BPF instructions
*
* this function is called after eBPF program passed verification
*/
static int fixup_bpf_calls(struct bpf_verifier_env *env)
{
struct bpf_prog *prog = env->prog;
struct bpf_insn *insn = prog->insnsi;
const struct bpf_func_proto *fn;
const int insn_cnt = prog->len;
struct bpf_insn insn_buf[16];
struct bpf_prog *new_prog;
struct bpf_map *map_ptr;
int i, cnt, delta = 0;
for (i = 0; i < insn_cnt; i++, insn++) {
if (insn->code != (BPF_JMP | BPF_CALL))
continue;
if (insn->imm == BPF_FUNC_get_route_realm)
prog->dst_needed = 1;
if (insn->imm == BPF_FUNC_get_prandom_u32)
bpf_user_rnd_init_once();
if (insn->imm == BPF_FUNC_tail_call) {
/* If we tail call into other programs, we
* cannot make any assumptions since they can
* be replaced dynamically during runtime in
* the program array.
*/
prog->cb_access = 1;
env->prog->aux->stack_depth = MAX_BPF_STACK;
/* mark bpf_tail_call as different opcode to avoid
* conditional branch in the interpeter for every normal
* call and to prevent accidental JITing by JIT compiler
* that doesn't support bpf_tail_call yet
*/
insn->imm = 0;
insn->code = BPF_JMP | BPF_TAIL_CALL;
continue;
}
if (ebpf_jit_enabled() && insn->imm == BPF_FUNC_map_lookup_elem) {
map_ptr = env->insn_aux_data[i + delta].map_ptr;
if (map_ptr == BPF_MAP_PTR_POISON ||
!map_ptr->ops->map_gen_lookup)
goto patch_call_imm;
cnt = map_ptr->ops->map_gen_lookup(map_ptr, insn_buf);
if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
verbose("bpf verifier is misconfigured\n");
return -EINVAL;
}
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf,
cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
/* keep walking new program and skip insns we just inserted */
env->prog = prog = new_prog;
insn = new_prog->insnsi + i + delta;
continue;
}
patch_call_imm:
fn = prog->aux->ops->get_func_proto(insn->imm);
/* all functions that have prototype and verifier allowed
* programs to call them, must be real in-kernel functions
*/
if (!fn->func) {
verbose("kernel subsystem misconfigured func %s#%d\n",
func_id_name(insn->imm), insn->imm);
return -EFAULT;
}
insn->imm = fn->func - __bpf_call_base;
}
return 0;
}
static void free_states(struct bpf_verifier_env *env)
{
struct bpf_verifier_state_list *sl, *sln;
int i;
if (!env->explored_states)
return;
for (i = 0; i < env->prog->len; i++) {
sl = env->explored_states[i];
if (sl)
while (sl != STATE_LIST_MARK) {
sln = sl->next;
kfree(sl);
sl = sln;
}
}
kfree(env->explored_states);
}
int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
{
char __user *log_ubuf = NULL;
struct bpf_verifier_env *env;
int ret = -EINVAL;
/* 'struct bpf_verifier_env' can be global, but since it's not small,
* allocate/free it every time bpf_check() is called
*/
env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
if (!env)
return -ENOMEM;
env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) *
(*prog)->len);
ret = -ENOMEM;
if (!env->insn_aux_data)
goto err_free_env;
env->prog = *prog;
/* grab the mutex to protect few globals used by verifier */
mutex_lock(&bpf_verifier_lock);
if (attr->log_level || attr->log_buf || attr->log_size) {
/* user requested verbose verifier output
* and supplied buffer to store the verification trace
*/
log_level = attr->log_level;
log_ubuf = (char __user *) (unsigned long) attr->log_buf;
log_size = attr->log_size;
log_len = 0;
ret = -EINVAL;
/* log_* values have to be sane */
if (log_size < 128 || log_size > UINT_MAX >> 8 ||
log_level == 0 || log_ubuf == NULL)
goto err_unlock;
ret = -ENOMEM;
log_buf = vmalloc(log_size);
if (!log_buf)
goto err_unlock;
} else {
log_level = 0;
}
env->strict_alignment = !!(attr->prog_flags & BPF_F_STRICT_ALIGNMENT);
if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
env->strict_alignment = true;
ret = replace_map_fd_with_map_ptr(env);
if (ret < 0)
goto skip_full_check;
env->explored_states = kcalloc(env->prog->len,
sizeof(struct bpf_verifier_state_list *),
GFP_USER);
ret = -ENOMEM;
if (!env->explored_states)
goto skip_full_check;
ret = check_cfg(env);
if (ret < 0)
goto skip_full_check;
env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
ret = do_check(env);
skip_full_check:
while (pop_stack(env, NULL) >= 0);
free_states(env);
if (ret == 0)
/* program is valid, convert *(u32*)(ctx + off) accesses */
ret = convert_ctx_accesses(env);
if (ret == 0)
ret = fixup_bpf_calls(env);
if (log_level && log_len >= log_size - 1) {
BUG_ON(log_len >= log_size);
/* verifier log exceeded user supplied buffer */
ret = -ENOSPC;
/* fall through to return what was recorded */
}
/* copy verifier log back to user space including trailing zero */
if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
ret = -EFAULT;
goto free_log_buf;
}
if (ret == 0 && env->used_map_cnt) {
/* if program passed verifier, update used_maps in bpf_prog_info */
env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
sizeof(env->used_maps[0]),
GFP_KERNEL);
if (!env->prog->aux->used_maps) {
ret = -ENOMEM;
goto free_log_buf;
}
memcpy(env->prog->aux->used_maps, env->used_maps,
sizeof(env->used_maps[0]) * env->used_map_cnt);
env->prog->aux->used_map_cnt = env->used_map_cnt;
/* program is valid. Convert pseudo bpf_ld_imm64 into generic
* bpf_ld_imm64 instructions
*/
convert_pseudo_ld_imm64(env);
}
free_log_buf:
if (log_level)
vfree(log_buf);
if (!env->prog->aux->used_maps)
/* if we didn't copy map pointers into bpf_prog_info, release
* them now. Otherwise free_bpf_prog_info() will release them.
*/
release_maps(env);
*prog = env->prog;
err_unlock:
mutex_unlock(&bpf_verifier_lock);
vfree(env->insn_aux_data);
err_free_env:
kfree(env);
return ret;
}
int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops,
void *priv)
{
struct bpf_verifier_env *env;
int ret;
env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
if (!env)
return -ENOMEM;
env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) *
prog->len);
ret = -ENOMEM;
if (!env->insn_aux_data)
goto err_free_env;
env->prog = prog;
env->analyzer_ops = ops;
env->analyzer_priv = priv;
/* grab the mutex to protect few globals used by verifier */
mutex_lock(&bpf_verifier_lock);
log_level = 0;
env->strict_alignment = false;
if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
env->strict_alignment = true;
env->explored_states = kcalloc(env->prog->len,
sizeof(struct bpf_verifier_state_list *),
GFP_KERNEL);
ret = -ENOMEM;
if (!env->explored_states)
goto skip_full_check;
ret = check_cfg(env);
if (ret < 0)
goto skip_full_check;
env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
ret = do_check(env);
skip_full_check:
while (pop_stack(env, NULL) >= 0);
free_states(env);
mutex_unlock(&bpf_verifier_lock);
vfree(env->insn_aux_data);
err_free_env:
kfree(env);
return ret;
}
EXPORT_SYMBOL_GPL(bpf_analyzer);
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