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

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From: Marco Elver <elver@xxxxxxxxxx>
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/0000000000003f654905c168b09d@xxxxxxxxxx, which
was not detectable by software KASAN modes.

Link: https://lkml.kernel.org/r/20211119142219.1519617-1-elver@xxxxxxxxxx
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

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

--- 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();
_



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