Re: CVE-2025-40146: blk-mq: fix potential deadlock while nr_requests grown

[Zheng Qixing]

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@xxxxxxxxxxxxx/
> 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