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mm: kfence: disable KMSAN when checking the canary

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KMSAN warns about check_canary() accessing the canary.

The reason is that, even though set_canary() is properly instrumented and
sets shadow, slub explicitly poisons the canary's address range
afterwards.

Unpoisoning the canary is not the right thing to do: only check_canary()
is supposed to ever touch it.  Instead, disable KMSAN checks around canary
read accesses.

Link: https://lkml.kernel.org/r/20240621113706.315500-20-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Tested-by: Alexander Potapenko <glider@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <kasan-dev@googlegroups.com>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ilya Leoshkevich 2024-06-21 13:35:03 +02:00 committed by Andrew Morton
parent adea987618
commit 4d7b5a2cec
1 changed files with 9 additions and 2 deletions
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11
mm/kfence/core.c
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@ -305,8 +305,14 @@ metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state nex
WRITE_ONCE(meta->state, next);
}
#ifdef CONFIG_KMSAN
#define check_canary_attributes noinline __no_kmsan_checks
#else
#define check_canary_attributes inline
#endif
/* Check canary byte at @addr. */
static inline bool check_canary_byte(u8 *addr)
static check_canary_attributes bool check_canary_byte(u8 *addr)
{
struct kfence_metadata *meta;
unsigned long flags;
@ -341,7 +347,8 @@ static inline void set_canary(const struct kfence_metadata *meta)
*((u64 *)addr) = KFENCE_CANARY_PATTERN_U64;
}
static inline void check_canary(const struct kfence_metadata *meta)
static check_canary_attributes void
check_canary(const struct kfence_metadata *meta)
{
const unsigned long pageaddr = ALIGN_DOWN(meta->addr, PAGE_SIZE);
unsigned long addr = pageaddr;