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From: Matt Fleming <matt@readmodwrite.com>
To: Tejun Heo <tj@kernel.org>
Cc: David Vernet <void@manifault.com>,
	Andrea Righi <arighi@nvidia.com>,
	 Changwoo Min <changwoo@igalia.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	 Suren Baghdasaryan <surenb@google.com>,
	Peter Zijlstra <peterz@infradead.org>,
	 Edward Adam Davis <eadavis@qq.com>,
	Chen Ridong <chenridong@huaweicloud.com>,
	 Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
	"ziwei . dai" <ziwei.dai@unisoc.com>,
	 "ke . wang" <ke.wang@unisoc.com>,
	Matt Fleming <mfleming@cloudflare.com>,
	 sched-ext@lists.linux.dev, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org,  stable@vger.kernel.org,
	kernel-team@cloudflare.com
Subject: Re: [PATCHSET v2] sched/psi: Fix psimon fork deadlock and rtpoll_timer UAF
Date: Mon, 13 Jul 2026 14:49:55 +0100	[thread overview]
Message-ID: <alTs1drVX4kb124h@matt-Precision-5490> (raw)
In-Reply-To: <20260712174619.3553231-1-tj@kernel.org>

On Sun, Jul 12, 2026 at 07:46:17AM -1000, Tejun Heo wrote:
> Hello,
> 
> v2: - Retagged sched/psi (was cgroup) (patch 1).
>     - Added a fix for a pre-existing rtpoll_timer use-after-free that the
>       Sashiko AI review flagged on the previous posting (patch 2).
> 
> v1: https://lore.kernel.org/r/20260710134945-psimon-fix-tj@kernel.org
> 
> a5b98009f16d ("sched/psi: fix race between file release and pressure
> write") made pressure_write() fork the psimon kthread while holding
> cgroup_mutex, which deadlocks against the sched_ext enable path blocking
> forks before grabbing cgroup_mutex. Patch 1 moves the fork outside
> cgroup_mutex. Patch 2 fixes the use-after-free from a schedule attempt
> re-arming group->rtpoll_timer behind psi_trigger_destroy() by shutting
> down the timer when the group is freed.
> 
> Matt, patch 1 is unchanged from the previous posting except for the
> subject prefix, so test results against that posting still apply.

I ended up testing both patches. This resolves the issue for me!

Thanks,
Matt

      parent reply	other threads:[~2026-07-13 13:49 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-12 17:46 [PATCHSET v2] sched/psi: Fix psimon fork deadlock and rtpoll_timer UAF Tejun Heo
2026-07-12 17:46 ` [PATCH 1/2] sched/psi: Create the psimon kthread outside of cgroup_mutex Tejun Heo
2026-07-13 10:51   ` Johannes Weiner
2026-07-13 13:48   ` Matt Fleming
2026-07-13 15:19     ` Suren Baghdasaryan
2026-07-12 17:46 ` [PATCH 2/2] sched/psi: Shut down rtpoll_timer in psi_cgroup_free() Tejun Heo
2026-07-13 10:56   ` Johannes Weiner
2026-07-13 14:07     ` Suren Baghdasaryan
2026-07-13 15:19       ` Suren Baghdasaryan
2026-07-13 13:48   ` Matt Fleming
2026-07-13 13:49 ` Matt Fleming [this message]

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