From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Daehyeon Ko <4ncienth@gmail.com>, Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched/autogroup: Fix task_group UAF during thread creation
Date: Fri, 30 Oct 2026 16:28:54 -1000 [thread overview]
Message-ID: <36ce43428e53d1d6e47dddb43697ccf2@kernel.org> (raw)
In-Reply-To: <20261030154940.GW2668564@noisy.programming.kicks-ass.net>
Hello, Peter.
On Fri, Oct 30, 2026 at 04:49:40PM +0100, Peter Zijlstra wrote:
> Now, AUTOGROUP depends on CGROUP, so we can make autogroup_move_group()
> also use cgroup_threadgroup_rwsem, such that the autogroup and cgroup
> logic stays the same?
cgroup_threadgroup_rwsem is a global percpu rwsem and taking it for
write on a regular basis can be really expensive.
> I mean, yes we can move sched_core_fork() into the siglock region, but
> duplicating most of sched_cgroup_fork() in there just to fix an
> autogroup thingy seems weird and inconsistent.
Either way, AFAICS, autogroup doesn't need cgroup_threadgroup_rwsem. The
cgroup side has to be settled early in fork, but the autogroup side
doesn't. Can't we just move the autogroup assignment later in fork, to a
point where it can't race against setsid()?
Thanks.
--
tejun
prev parent reply other threads:[~2026-10-31 2:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-23 1:36 Daehyeon Ko
2026-10-26 11:57 ` Peter Zijlstra
2026-10-30 3:45 ` Daehyeon Ko
2026-10-30 15:49 ` Peter Zijlstra
2026-10-31 2:28 ` Tejun Heo [this message]
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