[037/146] kasan: add ability to detect double-kmem_cache_destroy()

Commit Message

Andrew Morton Jan. 14, 2022, 10:04 p.m. UTC

From: Marco Elver <[e-mail]>
Subject: kasan: add ability to detect double-kmem_cache_destroy()

Because mm/slab_common.c is not instrumented with software KASAN modes, it
is not possible to detect use-after-free of the kmem_cache passed into
kmem_cache_destroy().  In particular, because of the s->refcount-- and
subsequent early return if non-zero, KASAN would never be able to see the
double-free via kmem_cache_free(kmem_cache, s).  To be able to detect a
double-kmem_cache_destroy(), check accessibility of the kmem_cache, and in
case of failure return early.

While KASAN_HW_TAGS is able to detect such bugs, by checking accessibility
and returning early we fail more gracefully and also avoid corrupting
reused objects (where tags mismatch).

A recent case of a double-kmem_cache_destroy() was detected by KFENCE:
https://lkml.kernel.org/r/[e-mail], which
was not detectable by software KASAN modes.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Marco Elver <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Reviewed-by: Andrey Konovalov <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/slab_common.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

--- a/mm/slab_common.c~kasan-add-ability-to-detect-double-kmem_cache_destroy
+++ a/mm/slab_common.c
@@ -489,7 +489,7 @@  void slab_kmem_cache_release(struct kmem
 
 void kmem_cache_destroy(struct kmem_cache *s)
 {
-	if (unlikely(!s))
+	if (unlikely(!s) || !kasan_check_byte(s))
 		return;
 
 	cpus_read_lock();