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kasan: report only the first error by default

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Disable kasan after the first report.  There are several reasons for
this:

 - Single bug quite often has multiple invalid memory accesses causing
   storm in the dmesg.

 - Write OOB access might corrupt metadata so the next report will print
   bogus alloc/free stacktraces.

 - Reports after the first easily could be not bugs by itself but just
   side effects of the first one.

Given that multiple reports usually only do harm, it makes sense to
disable kasan after the first one.  If user wants to see all the
reports, the boot-time parameter kasan_multi_shot must be used.

[[email protected]: wrote changelog and doc, added missing include]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Mark Rutland <[email protected]>
Signed-off-by: Andrey Ryabinin <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Mark Rutland 2017-03-31 15:12:04 -07:00 • committed by Linus Torvalds
commit b0845ce583
5 changed files with 55 additions and 5 deletions
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5
mm/kasan/kasan.h
View file

@ -96,11 +96,6 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
<< KASAN_SHADOW_SCALE_SHIFT);
}
static inline bool kasan_report_enabled(void)
{
return !current->kasan_depth;
}
void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip);
void kasan_report_double_free(struct kmem_cache *cache, void *object,

36
mm/kasan/report.c
View file

@ -13,7 +13,9 @@
*
*/
#include <linux/bitops.h>
#include <linux/ftrace.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/printk.h>
@ -293,6 +295,40 @@ static void kasan_report_error(struct kasan_access_info *info)
kasan_end_report(&flags);
}
static unsigned long kasan_flags;
#define KASAN_BIT_REPORTED 0
#define KASAN_BIT_MULTI_SHOT 1
bool kasan_save_enable_multi_shot(void)
{
return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
}
EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
void kasan_restore_multi_shot(bool enabled)
{
if (!enabled)
clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
}
EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
static int __init kasan_set_multi_shot(char *str)
{
set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
return 1;
}
__setup("kasan_multi_shot", kasan_set_multi_shot);
static inline bool kasan_report_enabled(void)
{
if (current->kasan_depth)
return false;
if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
return true;
return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
}
void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip)
{