linux-kernel - Re: [PATCH] kernfs: Fix UAF in PSI polling when open file is released

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <38ef3ff9-b380-44f0-9315-8b3714b0948d@huaweicloud.com>
Date: Fri, 22 Aug 2025 09:57:51 +0800
From: Chen Ridong <chenridong@...weicloud.com>
To: Tejun Heo <tj@...nel.org>
Cc: Baokun Li <libaokun1@...wei.com>, cgroups@...r.kernel.org,
 chenridong@...wei.com, gregkh@...uxfoundation.org, hannes@...xchg.org,
 linux-kernel@...r.kernel.org, lujialin4@...wei.com, mkoutny@...e.com,
 peterz@...radead.org, zhouchengming@...edance.com,
 Yang Erkun <yangerkun@...wei.com>
Subject: Re: [PATCH] kernfs: Fix UAF in PSI polling when open file is released



On 2025/8/20 9:46, Tejun Heo wrote:
> Hello,
> 
> On Mon, Aug 18, 2025 at 04:00:08PM +0800, Chen Ridong wrote:
>>> A potential solution is to make the lifecycles of cgroup_file_ctx and
>>> psi_trigger match the struct kernfs_open_file they're associated with.
>>> Maybe we could just get rid of the kernfs_release_file call in
>>> kernfs_drain_open_files?
>>>
>>
>> Hi, Tj, what do you think about this solution?
> 
> So, I think it's really fragile for a killed (drained) kernfs_open_file to
> be reused after the corresponding @kn is resurrected. Once killed, that file
> should stay dead. I think it'd be best if we can do this in a generic manner
> rather than trying to fix it only for poll.
> 
> kernfs_get_active() is the thing which gates active operations on the file.
> Maybe we can add a wrapper, say, kernfs_get_active_of(struct
> kernfs_open_file *of) which returns NULL if @of has already been killed or
> the underlying @kn can't be activated?
> 
> Thanks.
> 

Thank you Tj,

This is reasonable, I will try.

-- 
Best regards,
Ridong