linux-kernel - Re: CVE-2025-40146: blk-mq: fix potential deadlock while nr

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Message-ID: <82df4ae1-2940-4214-b46e-a2f8242b3582@huaweicloud.com>
Date: Fri, 28 Nov 2025 09:15:22 +0800
From: Zheng Qixing <zhengqixing@...weicloud.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: cve@...nel.org, linux-kernel@...r.kernel.org, yukuai@...as.com,
 ming.lei@...hat.com, Nilay Shroff <nilay@...ux.ibm.com>,
 "zhangyi (F)" <yi.zhang@...wei.com>, yangerkun <yangerkun@...wei.com>,
 Hou Tao <houtao1@...wei.com>
Subject: Re: CVE-2025-40146: blk-mq: fix potential deadlock while nr_requests
 grown


在 2025/11/27 21:39, Greg KH 写道:
> On Thu, Nov 27, 2025 at 09:22:42PM +0800, Zheng Qixing wrote:
>> Hi,
>>
>> Commit b86433721f46 ("blk-mq: fix potential deadlock while nr_requests
>> grown")  aims to avoid a deadlock issue when the queue is frozen and memory
>> reclaim is triggered.
>>
>> However, the sysfs nr_requests update path is already under a
>> memalloc_noio_save() region while the queue is frozen (via
>> blk_mq_freeze_queue()).
> Did the lockdep splat in
> https://lore.kernel.org/all/0659ea8d-a463-47c8-9180-43c719e106eb@linux.ibm.com/
> not describe the issue here that the commit is attempting to solve?
>
> thanks,
>
> greg k-h


The deadlock issue described in this link is about elevator switch path, 
but the patch modifies sysfs nr_requests update path.

I didn't identify any potential deadlock issues on this path. If I 
misunderstood something, could someone help clarify?


Thanks,

Qixing