linux-kernel - [PATCH 2/3] slab: don't put freepointer outside of object if only orig

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Date: Tue, 28 May 2024 15:16:47 +0800
From: Chengming Zhou <chengming.zhou@...ux.dev>
To: Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, 
 David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, 
 Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, 
 Hyeonggon Yoo <42.hyeyoo@...il.com>, Feng Tang <feng.tang@...el.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
 zhouchengming@...edance.com, Chengming Zhou <chengming.zhou@...ux.dev>
Subject: [PATCH 2/3] slab: don't put freepointer outside of object if only
 orig_size

The commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra
allocated kmalloc space than requested") will extend right redzone
when allocating for orig_size < object_size. So we can't overlay the
freepointer in the object space in this case.

But the code looks like it forgot to check SLAB_RED_ZONE, since there
won't be extended right redzone if only orig_size enabled.

Signed-off-by: Chengming Zhou <chengming.zhou@...ux.dev>
---
 mm/slub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index de57512734ac..b92d9a557852 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5150,7 +5150,7 @@ static int calculate_sizes(struct kmem_cache *s)
 	 */
 	s->inuse = size;
 
-	if (slub_debug_orig_size(s) ||
+	if (((flags & SLAB_RED_ZONE) && slub_debug_orig_size(s)) ||
 	    (flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) ||
 	    ((flags & SLAB_RED_ZONE) && s->object_size < sizeof(void *)) ||
 	    s->ctor) {

-- 
2.45.1