linux-kernel - Re: [PATCH V3] cgroup/cpuset: Prevent UAF in proc_cpuset

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Date: Thu, 27 Jun 2024 14:37:35 -0400
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>, Michal Koutný
 <mkoutny@...e.com>
Cc: Chen Ridong <chenridong@...wei.com>, lizefan.x@...edance.com,
 hannes@...xchg.org, adityakali@...gle.com, sergeh@...nel.org,
 cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] cgroup/cpuset: Prevent UAF in proc_cpuset_show()


On 6/27/24 14:29, Tejun Heo wrote:
> Hello,
>
> On Thu, Jun 27, 2024 at 11:46:10AM +0200, Michal Koutný wrote:
>> Your patch should work thanks to the rcu_read_lock and
>> cgroup_free_root/kfree_rcu and the `if (css->cgroup)` guard is
>> unnecessary.

I also notice that the if (css->cgroup) guard is not needed. I didn't 
reject it because it doesn't hurt.

Cheers,
Longman

>>
>> So the patch is a functional fix, the reasoning in commit message is
>> little off. Not sure if Tejun rebases his for-6.10-fixes (with a
>> possible v4), full fixup commit for this may not be worthy.
> This one's on the top. If Chen can send me a patch with updated description,
> I will replace the patch.
>
> Thanks.
>