![Josef Bacik](/assets/img/avatar_default.png)
Suppose you have a map array value that is something like this struct foo { unsigned iter; int array[SOME_CONSTANT]; }; You can easily insert this into an array, but you cannot modify the contents of foo->array[] after the fact. This is because we have no way to verify we won't go off the end of the array at verification time. This patch provides a start for this work. We accomplish this by keeping track of a minimum and maximum value a register could be while we're checking the code. Then at the time we try to do an access into a MAP_VALUE we verify that the maximum offset into that region is a valid access into that memory region. So in practice, code such as this unsigned index = 0; if (foo->iter >= SOME_CONSTANT) foo->iter = index; else index = foo->iter++; foo->array[index] = bar; would be allowed, as we can verify that index will always be between 0 and SOME_CONSTANT-1. If you wish to use signed values you'll have to have an extra check to make sure the index isn't less than 0, or do something like index %= SOME_CONSTANT. Signed-off-by: Josef Bacik <jbacik@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
103 lines
3.2 KiB
C
103 lines
3.2 KiB
C
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
|
|
*
|
|
* 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.
|
|
*/
|
|
#ifndef _LINUX_BPF_VERIFIER_H
|
|
#define _LINUX_BPF_VERIFIER_H 1
|
|
|
|
#include <linux/bpf.h> /* for enum bpf_reg_type */
|
|
#include <linux/filter.h> /* for MAX_BPF_STACK */
|
|
|
|
/* Just some arbitrary values so we can safely do math without overflowing and
|
|
* are obviously wrong for any sort of memory access.
|
|
*/
|
|
#define BPF_REGISTER_MAX_RANGE (1024 * 1024 * 1024)
|
|
#define BPF_REGISTER_MIN_RANGE -(1024 * 1024 * 1024)
|
|
|
|
struct bpf_reg_state {
|
|
enum bpf_reg_type type;
|
|
/*
|
|
* Used to determine if any memory access using this register will
|
|
* result in a bad access.
|
|
*/
|
|
u64 min_value, max_value;
|
|
union {
|
|
/* valid when type == CONST_IMM | PTR_TO_STACK | UNKNOWN_VALUE */
|
|
s64 imm;
|
|
|
|
/* valid when type == PTR_TO_PACKET* */
|
|
struct {
|
|
u32 id;
|
|
u16 off;
|
|
u16 range;
|
|
};
|
|
|
|
/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
|
|
* PTR_TO_MAP_VALUE_OR_NULL
|
|
*/
|
|
struct bpf_map *map_ptr;
|
|
};
|
|
};
|
|
|
|
enum bpf_stack_slot_type {
|
|
STACK_INVALID, /* nothing was stored in this stack slot */
|
|
STACK_SPILL, /* register spilled into stack */
|
|
STACK_MISC /* BPF program wrote some data into this slot */
|
|
};
|
|
|
|
#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
|
|
|
|
/* state of the program:
|
|
* type of all registers and stack info
|
|
*/
|
|
struct bpf_verifier_state {
|
|
struct bpf_reg_state regs[MAX_BPF_REG];
|
|
u8 stack_slot_type[MAX_BPF_STACK];
|
|
struct bpf_reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
|
|
};
|
|
|
|
/* linked list of verifier states used to prune search */
|
|
struct bpf_verifier_state_list {
|
|
struct bpf_verifier_state state;
|
|
struct bpf_verifier_state_list *next;
|
|
};
|
|
|
|
struct bpf_insn_aux_data {
|
|
enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
|
|
};
|
|
|
|
#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
|
|
|
|
struct bpf_verifier_env;
|
|
struct bpf_ext_analyzer_ops {
|
|
int (*insn_hook)(struct bpf_verifier_env *env,
|
|
int insn_idx, int prev_insn_idx);
|
|
};
|
|
|
|
/* single container for all structs
|
|
* one verifier_env per bpf_check() call
|
|
*/
|
|
struct bpf_verifier_env {
|
|
struct bpf_prog *prog; /* eBPF program being verified */
|
|
struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
|
|
int stack_size; /* number of states to be processed */
|
|
struct bpf_verifier_state cur_state; /* current verifier state */
|
|
struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
|
|
const struct bpf_ext_analyzer_ops *analyzer_ops; /* external analyzer ops */
|
|
void *analyzer_priv; /* pointer to external analyzer's private data */
|
|
struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
|
|
u32 used_map_cnt; /* number of used maps */
|
|
u32 id_gen; /* used to generate unique reg IDs */
|
|
bool allow_ptr_leaks;
|
|
bool seen_direct_write;
|
|
bool varlen_map_value_access;
|
|
struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
|
|
};
|
|
|
|
int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops,
|
|
void *priv);
|
|
|
|
#endif /* _LINUX_BPF_VERIFIER_H */
|