From: "Lin, Zhenpeng" <zplin@psu.edu> To: unlisted-recipients:; (no To-header on input) Cc: Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Kees Cook <keescook@chromium.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org> Subject: [PATCH] slub: choose the right freelist pointer location when creating small caches Date: Sat, 5 Jun 2021 01:58:13 +0000 [thread overview] Message-ID: <6746FEEA-FD69-4792-8DDA-C78F5FE7DA02@psu.edu> (raw) When enabling CONFIG_SLUB_DEBUG and booting with "slub_debug=Z", the kernel crashes at creating caches if the object size is smaller than 2*sizeof(void*). The problem is due to the wrong calculation of freepointer_area. The freelist pointer can be stored in the middle of object only if the object size is not smaller than 2*sizeof(void*). Otherwise, the freelist pointer will be corrupted by SLUB_RED_ZONE. Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object") Fixes: 89b83f282d8b ("slub: avoid redzone when choosing freepointer location") Signed-off-by: Zhenpeng Lin <zplin@psu.edu> --- mm/slub.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 3f96e099817a..cb23233ee683 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3704,7 +3704,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order) * can't use that portion for writing the freepointer, so * s->offset must be limited within this for the general case. */ - freepointer_area = size; + freepointer_area = s->object_size; #ifdef CONFIG_SLUB_DEBUG /* @@ -3751,7 +3751,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order) */ s->offset = size; size += sizeof(void *); - } else if (freepointer_area > sizeof(void *)) { + } else if (freepointer_area >= 2 * sizeof(void *)) { /* * Store freelist pointer near middle of object to keep * it away from the edges of the object to avoid small -- 2.17.1
WARNING: multiple messages have this Message-ID (diff)
From: "Lin, Zhenpeng" <zplin@psu.edu> Cc: Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Kees Cook <keescook@chromium.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org> Subject: [PATCH] slub: choose the right freelist pointer location when creating small caches Date: Sat, 5 Jun 2021 01:58:13 +0000 [thread overview] Message-ID: <6746FEEA-FD69-4792-8DDA-C78F5FE7DA02@psu.edu> (raw) When enabling CONFIG_SLUB_DEBUG and booting with "slub_debug=Z", the kernel crashes at creating caches if the object size is smaller than 2*sizeof(void*). The problem is due to the wrong calculation of freepointer_area. The freelist pointer can be stored in the middle of object only if the object size is not smaller than 2*sizeof(void*). Otherwise, the freelist pointer will be corrupted by SLUB_RED_ZONE. Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object") Fixes: 89b83f282d8b ("slub: avoid redzone when choosing freepointer location") Signed-off-by: Zhenpeng Lin <zplin@psu.edu> --- mm/slub.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 3f96e099817a..cb23233ee683 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3704,7 +3704,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order) * can't use that portion for writing the freepointer, so * s->offset must be limited within this for the general case. */ - freepointer_area = size; + freepointer_area = s->object_size; #ifdef CONFIG_SLUB_DEBUG /* @@ -3751,7 +3751,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order) */ s->offset = size; size += sizeof(void *); - } else if (freepointer_area > sizeof(void *)) { + } else if (freepointer_area >= 2 * sizeof(void *)) { /* * Store freelist pointer near middle of object to keep * it away from the edges of the object to avoid small -- 2.17.1
next reply other threads:[~2021-06-05 1:58 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-05 1:58 Lin, Zhenpeng [this message] 2021-06-05 1:58 ` [PATCH] slub: choose the right freelist pointer location when creating small caches Lin, Zhenpeng 2021-06-08 18:26 ` Kees Cook 2021-06-08 18:33 ` Lin, Zhenpeng 2021-06-08 18:41 ` Kees Cook 2021-06-08 19:06 ` Lin, Zhenpeng 2021-06-08 23:14 ` Kees Cook 2021-06-10 20:20 ` Lin, Zhenpeng 2021-06-10 23:01 ` Kees Cook 2021-06-11 4:22 ` Lin, Zhenpeng
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