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mm: slub: disable KMSAN when checking the padding bytes

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Even though the KMSAN warnings generated by memchr_inv() are suppressed by
metadata_access_enable(), its return value may still be poisoned.

The reason is that the last iteration of memchr_inv() returns `*start !=
value ?  start : NULL`, where *start is poisoned.  Because of this,
somewhat counterintuitively, the shadow value computed by
visitSelectInst() is equal to `(uintptr_t)start`.

One possibility to fix this, since the intention behind guarding
memchr_inv() behind metadata_access_enable() is to touch poisoned metadata
without triggering KMSAN, is to unpoison its return value.  However, this
approach is too fragile.  So simply disable the KMSAN checks in the
respective functions.

Link: https://lkml.kernel.org/r/20240621113706.315500-19-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-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 13:35:02 +02:00 committed by Andrew Morton
parent 0e9a8550f3
commit adea987618
1 changed files with 12 additions and 4 deletions
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16
mm/slub.c
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@ -1176,9 +1176,16 @@ static void restore_bytes(struct kmem_cache *s, char *message, u8 data,
memset(from, data, to - from);
}
static int check_bytes_and_report(struct kmem_cache *s, struct slab *slab,
u8 *object, char *what,
u8 *start, unsigned int value, unsigned int bytes)
#ifdef CONFIG_KMSAN
#define pad_check_attributes noinline __no_kmsan_checks
#else
#define pad_check_attributes
#endif
static pad_check_attributes int
check_bytes_and_report(struct kmem_cache *s, struct slab *slab,
u8 *object, char *what,
u8 *start, unsigned int value, unsigned int bytes)
{
u8 *fault;
u8 *end;
@ -1270,7 +1277,8 @@ static int check_pad_bytes(struct kmem_cache *s, struct slab *slab, u8 *p)
}
/* Check the pad bytes at the end of a slab page */
static void slab_pad_check(struct kmem_cache *s, struct slab *slab)
static pad_check_attributes void
slab_pad_check(struct kmem_cache *s, struct slab *slab)
{
u8 *start;
u8 *fault;