From: Harry Yoo <harry.yoo@oracle.com>
To: Hao Ge <hao.ge@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@gentwo.org>,
David Rientjes <rientjes@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Suren Baghdasaryan <surenb@google.com>,
Shakeel Butt <shakeel.butt@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Hao Ge <gehao@kylinos.cn>,
stable@vger.kernel.org
Subject: Re: [PATCH v3] slab: Avoid race on slab->obj_exts in alloc_slab_obj_exts
Date: Tue, 21 Oct 2025 11:16:29 +0900 [thread overview]
Message-ID: <aPbs_cu261GnQgcu@hyeyoo> (raw)
In-Reply-To: <20251021010353.1187193-1-hao.ge@linux.dev>
On Tue, Oct 21, 2025 at 09:03:53AM +0800, Hao Ge wrote:
> From: Hao Ge <gehao@kylinos.cn>
>
> If two competing threads enter alloc_slab_obj_exts() and one of them
> fails to allocate the object extension vector, it might override the
> valid slab->obj_exts allocated by the other thread with
> OBJEXTS_ALLOC_FAIL. This will cause the thread that lost this race and
> expects a valid pointer to dereference a NULL pointer later on.
>
> Update slab->obj_exts atomically using cmpxchg() to avoid
> slab->obj_exts overrides by racing threads.
>
> Thanks for Vlastimil and Suren's help with debugging.
>
> Fixes: f7381b911640 ("slab: mark slab->obj_exts allocation failures unconditionally")
> Cc: <stable@vger.kernel.org>
> Suggested-by: Suren Baghdasaryan <surenb@google.com>
> Signed-off-by: Hao Ge <gehao@kylinos.cn>
> ---
> v3: According to Suren's suggestion, simplify the commit message and the code comments.
> Thanks for Suren.
>
> v2: Incorporate handling for the scenario where, if mark_failed_objexts_alloc wins the race,
> the other process (that previously succeeded in allocation) will lose the race, based on Suren's suggestion.
> Add Suggested-by: Suren Baghdasaryan <surenb@google.com>
> ---
Looks good to me, thanks for fixing this!
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
--
Cheers,
Harry / Hyeonggon
next prev parent reply other threads:[~2025-10-21 2:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-21 1:03 Hao Ge
2025-10-21 2:16 ` Harry Yoo [this message]
2025-10-21 7:04 ` Vlastimil Babka
2025-10-21 13:24 ` Suren Baghdasaryan
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