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From: "Yu Kuai" <yukuai@fnnas.com>
To: "Zheng Qixing" <zhengqixing@huaweicloud.com>
Cc: <hch@infradead.org>, <cgroups@vger.kernel.org>,
	 <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	 <yi.zhang@huawei.com>, <yangerkun@huawei.com>,
	<houtao1@huawei.com>,  <tj@kernel.org>, <josef@toxicpanda.com>,
	<axboe@kernel.dk>,  <zhengqixing@huawei.com>, <yukuai@fnnas.com>
Subject: Re: [PATCH 2/3] blk-cgroup: fix uaf in blkcg_activate_policy() racing with blkg_free_workfn()
Date: Fri, 9 Jan 2026 14:43:39 +0800	[thread overview]
Message-ID: <22046287-0a36-45ac-bc17-b41636076552@fnnas.com> (raw)
In-Reply-To: <5fdbd368-6d00-4453-8f03-23d17c8c1338@huaweicloud.com>

Hi,

在 2026/1/9 14:22, Zheng Qixing 写道:
> I tried adding blkcg_mutex protection in blkcg_activate_policy() and 
> blkg_destroy_all() as suggested.
>
> Unfortunately, the UAF still occurs even with proper mutex protection.
>
> The mutex successfully protects the list structure during traversal 
> won't be added/removed from
>
> q->blkg_list while we hold the lock. However, this doesn't prevent the 
> same blkg from being released
>
> twice.

I don't understand, what I suggested should actually include your changes in this patch. Can you
show your changes and make sure blkcg_policy_teardown_pds() inside blkcg_activate_policy() is
also protected.

-- 
Thansk,
Kuai

  reply	other threads:[~2026-01-09  6:43 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-01-08  1:44 [PATCH 0/3] blk-cgroup: cleanup and bugfixs in blk-cgroup Zheng Qixing
2026-01-08  1:44 ` [PATCH 1/3] blk-cgroup: factor policy pd teardown loop into helper Zheng Qixing
2026-01-08 13:51   ` Christoph Hellwig
2026-01-08 16:12   ` Yu Kuai
2026-01-09 14:44   ` Michal Koutný
2026-01-12  1:04     ` Zheng Qixing
2026-01-08  1:44 ` [PATCH 2/3] blk-cgroup: fix uaf in blkcg_activate_policy() racing with blkg_free_workfn() Zheng Qixing
2026-01-08 13:51   ` Christoph Hellwig
2026-01-08 16:11   ` Yu Kuai
2026-01-09  6:22     ` Zheng Qixing
2026-01-09  6:43       ` Yu Kuai [this message]
2026-01-09  8:37         ` Zheng Qixing
2026-01-08  1:44 ` [PATCH 3/3] blk-cgroup: skip dying blkg in blkcg_activate_policy() Zheng Qixing
2026-01-08 13:52   ` Christoph Hellwig
2026-01-08 16:22   ` Yu Kuai
2026-01-09  8:46     ` Zheng Qixing

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