From: Vlastimil Babka <vbabka@suse.cz>
To: Chris Mason <clm@meta.com>, Rik van Riel <riel@surriel.com>
Cc: Pekka Enberg <penberg@kernel.org>,
Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
kernel-team@meta.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
David Rientjes <rientjes@google.com>,
kasan-dev <kasan-dev@googlegroups.com>,
Jann Horn <jannh@google.com>
Subject: Re: [PATCH] mm,slub: do not call do_slab_free for kfence object
Date: Tue, 30 Jul 2024 12:01:44 +0200 [thread overview]
Message-ID: <0d6e8252-de39-4414-b4e7-b6c22a427b0d@suse.cz> (raw)
In-Reply-To: <044edc48-f597-46dd-8dc8-524697e50848@meta.com>
On 7/29/24 8:46 PM, Chris Mason wrote:
>
>
> On 7/29/24 2:19 PM, Rik van Riel wrote:
>> In 782f8906f805 the freeing of kfence objects was moved from deep
>> inside do_free_slab to the wrapper functions outside. This is a nice
>> change, but unfortunately it missed one spot in __kmem_cache_free_bulk.
>>
>> This results in a crash like this:
>>
>> BUG skbuff_head_cache (Tainted: G S B E ): Padding overwritten. 0xffff88907fea0f00-0xffff88907fea0fff @offset=3840
>>
>> slab_err (mm/slub.c:1129)
>> free_to_partial_list (mm/slub.c:? mm/slub.c:4036)
>> slab_pad_check (mm/slub.c:864 mm/slub.c:1290)
>> check_slab (mm/slub.c:?)
>> free_to_partial_list (mm/slub.c:3171 mm/slub.c:4036)
>> kmem_cache_alloc_bulk (mm/slub.c:? mm/slub.c:4495 mm/slub.c:4586 mm/slub.c:4635)
>> napi_build_skb (net/core/skbuff.c:348 net/core/skbuff.c:527 net/core/skbuff.c:549)
>>
>> All the other callers to do_free_slab appear to be ok.
changed do_free_slab to do_slab_free in two places.
>>
>> Add a kfence_free check in __kmem_cache_free_bulk to avoid the crash.
>>
>> Reported-by: Chris Mason <clm@meta.com>
>> Fixes: 782f8906f805 ("mm/slub: free KFENCE objects in slab_free_hook()")
>> Cc: stable@kernel.org
>> Signed-off-by: Rik van Riel <riel@surriel.com>
>
> We found this after bisecting a slab corruption down to the kfence
> patch, and with this patch applied we're no longer falling over. So
> thanks Rik!
Indeed thanks and sorry for the trouble! Given that
__kmem_cache_free_bulk is currently only used to unwind a
kmem_cache_bulk_alloc() that runs out of memory in the middle of the
operation, I'm surprised you saw this happen reliably enough to bisect it.
Added to slab/for-6.11-rc1/fixes
> -chris
next prev parent reply other threads:[~2024-07-30 10:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-29 18:19 Rik van Riel
2024-07-29 18:46 ` Chris Mason
2024-07-30 10:01 ` Vlastimil Babka [this message]
2024-07-30 12:03 ` Chris Mason
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