linux-kernel - Re: [PATCH] kernel/sched: Fix sched_fork() access an invalid sched_task

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

Message-ID: <YTea0kK9yL5+GoKt@slm.duckdns.org>
Date:   Tue, 7 Sep 2021 07:01:06 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Zhang Qiao <zhangqiao22@...wei.com>
Cc:     peterz@...radead.org, juri.lelli@...hat.com,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        vincent.guittot@...aro.org
Subject: Re: [PATCH] kernel/sched: Fix sched_fork() access an invalid
 sched_task_group

Hello,

On Thu, Sep 02, 2021 at 03:42:15PM +0800, Zhang Qiao wrote:
> I checked the code again.
> I don't quite understand what you said, if the child be moved between
> cgroup_post_fork() and sched_post_sched(), what problems might it cause?

cgroup_post_fork() is where the child's creation is committed from cgroup's
POV, so it'd be migrating cgroups before the initial creation is finished.
>From glancing, looks like it'll break css_set task counts to begin with.
This violates the basic assumptions and can cause critical failures in
subtle ways. The would replace one subtle race with a possibly worse one.

Thanks.

-- 
tejun