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(); _
