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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5a09e348-9eeb-4502-9aa9-ef5da2f94218@suse.cz>
Date: Mon, 3 Jun 2024 11:25:45 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Chengming Zhou <chengming.zhou@...ux.dev>,
 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>,
 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
Subject: Re: [PATCH 2/3] slab: don't put freepointer outside of object if only
 orig_size

On 5/28/24 9:16 AM, Chengming Zhou wrote:
> 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>

Seems OK.

> ---
>  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 *)) ||

Should we consolidate the two cases with flags & SLAB_RED_ZONE?

Also below this is a comment that could also mention the slub_debug_orig_size().

>  	    s->ctor) {
>