[PATCH 13/32] kmsan: Support SLAB_POISON

Ilya Leoshkevich
2023-11-15T20:35:30Z

Avoid false KMSAN negatives with SLUB_DEBUG by allowing
kmsan_slab_free() to poison the freed memory, and by preventing
init_object() from unpoisoning new allocations.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
mm/kmsan/hooks.c | 2 +-
mm/slub.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 7b5814412e9f..7a30274b893c 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -76,7 +76,7 @@ void kmsan_slab_free(struct kmem_cache *s, void *object)
return;

/* RCU slabs could be legally used after free within the RCU period */
- if (unlikely(s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)))
+ if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU))
return;
/*
* If there's a constructor, freed memory must remain in the same state
diff --git a/mm/slub.c b/mm/slub.c
index 63d281dfacdb..8d9aa4d7cb7e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1024,7 +1024,8 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct slab *slab,
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
}

-static void init_object(struct kmem_cache *s, void *object, u8 val)
+__no_sanitize_memory static void
+init_object(struct kmem_cache *s, void *object, u8 val)
{
u8 *p = kasan_reset_tag(object);
unsigned int poison_size = s->object_size;
--
2.41.0