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From: Chengming Zhou <chengming.zhou@linux.dev>
Date: Tue, 28 May 2024 15:16:47 +0800
Subject: [PATCH 2/3] slab: don't put freepointer outside of object if only
 orig_size
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Message-Id: <20240528-b4-slab-debug-v1-2-8694ef4802df@linux.dev>
References: <20240528-b4-slab-debug-v1-0-8694ef4802df@linux.dev>
In-Reply-To: <20240528-b4-slab-debug-v1-0-8694ef4802df@linux.dev>
To: 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>, 
 Roman Gushchin <roman.gushchin@linux.dev>, 
 Hyeonggon Yoo <42.hyeyoo@gmail.com>, Feng Tang <feng.tang@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 
 zhouchengming@bytedance.com, Chengming Zhou <chengming.zhou@linux.dev>

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@linux.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