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From: Tejun Heo <tj@kernel.org>
To: Richard Clark <richard.xnu.clark@gmail.com>
Cc: jiangshanlai@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] workqueue: Prevent a new work item from queueing into a destruction wq
Date: Sun, 11 Dec 2022 20:23:49 -1000	[thread overview]
Message-ID: <Y5bI9ZbjpzNFpk/8@slm.duckdns.org> (raw)
In-Reply-To: <20221212061836.3620-1-richard.xnu.clark@gmail.com>

On Mon, Dec 12, 2022 at 02:18:36PM +0800, Richard Clark wrote:
> Currently the __WQ_DRAINING is used to prevent a new work item from queueing
> to a draining workqueue, but this flag will be cleared before the end of a
> RCU grace period. Because the workqueue instance is actually freed after
> the RCU grace period, this fact results in an opening window in which a new
> work item can be queued into a destorying workqueue and be scheduled
> consequently, for instance, the below code snippet demos this accident:

I mean, this is just use-after-free. The same scenario can happen with
non-RCU frees or if there happens to be an RCU grace period inbetween. I'm
not sure what's being protected here.

Thanks.

-- 
tejun

  reply	other threads:[~2022-12-12  6:23 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-12  6:18 Richard Clark
2022-12-12  6:23 ` Tejun Heo [this message]
2022-12-12  6:48   ` Lai Jiangshan
2022-12-12  9:26     ` richard clark
2022-12-12 22:27     ` Tejun Heo
2022-12-13  1:09       ` richard clark
2022-12-12  9:17   ` richard clark

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