linux-kernel - Re: [PATCH v2 1/3] blk-cgroup: fix race between policy activation and blkg destruction

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Message-ID: <2685a1b2-9c68-4b14-87bc-96c19a0a2e48@huaweicloud.com>
Date: Thu, 15 Jan 2026 13:32:56 +0800
From: Zheng Qixing <zhengqixing@...weicloud.com>
To: Michal Koutný <mkoutny@...e.com>
Cc: tj@...nel.org, josef@...icpanda.com, axboe@...nel.dk, yukuai3@...wei.com,
 hch@...radead.org, cgroups@...r.kernel.org, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com,
 houtao1@...wei.com, Zheng Qixing <zhengqixing@...wei.com>
Subject: Re: [PATCH v2 1/3] blk-cgroup: fix race between policy activation and
 blkg destruction

Resend...

blkcg_activate_policy()                blkg_free_workfn()
-------------------                    ------------------
spin_lock(&q->queue_lock)
...
if (!pd) {
     spin_unlock(&q->queue_lock)
     ...
     goto enomem
     }
enomem:
     spin_lock(&q->queue_lock)
     if (pd) {

                        ->pd_free_fn()  // pd freed

        pd->online // uaf
        ...
     }

                        spin_lock(&q->queue_lock)

                        list_del_init(&blkg->q_node)

                        spin_unlock(&q->queue_lock)