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x86/uaccess, kasan: Fix KASAN vs SMAP 

KASAN inserts extra code for every LOAD/STORE emitted by te compiler.
Much of this code is simple and safe to run with AC=1, however the
kasan_report() function, called on error, is most certainly not safe
to call with AC=1.

Therefore wrap kasan_report() in user_access_{save,restore}; which for
x86 SMAP, saves/restores EFLAGS and clears AC before calling the real
function.

Also ensure all the functions are without __fentry__ hook. The
function tracer is also not safe.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.2
Peter Zijlstra 2019-04-03 09:39:50 +02:00 committed by Ingo Molnar
parent a936af8ea3
commit 57b78a62e7
3 changed files with 14 additions and 2 deletions
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3
mm/kasan/Makefile
View File

@ -2,11 +2,13 @@
KASAN_SANITIZE := n
UBSAN_SANITIZE_common.o := n
UBSAN_SANITIZE_generic.o := n
UBSAN_SANITIZE_generic_report.o := n
UBSAN_SANITIZE_tags.o := n
KCOV_INSTRUMENT := n
CFLAGS_REMOVE_common.o = -pg
CFLAGS_REMOVE_generic.o = -pg
CFLAGS_REMOVE_generic_report.o = -pg
CFLAGS_REMOVE_tags.o = -pg
# Function splitter causes unnecessary splits in __asan_load1/__asan_store1
@ -14,6 +16,7 @@ CFLAGS_REMOVE_tags.o = -pg
CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
obj-$(CONFIG_KASAN) := common.o init.o report.o

10
mm/kasan/common.c
View File

@ -36,6 +36,7 @@
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/bug.h>
#include <linux/uaccess.h>
#include "kasan.h"
#include "../slab.h"
@ -614,6 +615,15 @@ void kasan_free_shadow(const struct vm_struct *vm)
vfree(kasan_mem_to_shadow(vm->addr));
}
extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);
void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
{
unsigned long flags = user_access_save();
__kasan_report(addr, size, is_write, ip);
user_access_restore(flags);
}
#ifdef CONFIG_MEMORY_HOTPLUG
static bool shadow_mapped(unsigned long addr)
{

3
mm/kasan/report.c
View File

@ -281,8 +281,7 @@ void kasan_report_invalid_free(void *object, unsigned long ip)
end_report(&flags);
}
void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip)
void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
{
struct kasan_access_info info;
void *tagged_addr;