From: Jens Axboe <axboe@kernel.dk>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Anvik Loitongbam <permissiontogallop@gmail.com>,
Pavel Begunkov <asml.silence@gmail.com>,
Olivier Langlois <olivier@trillion01.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
io-uring@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-rt-devel@lists.linux.dev, stable@vger.kernel.org
Subject: Re: [PATCH] io_uring/napi: fix list use-after-free on PREEMPT_RT
Date: Thu, 29 Oct 2026 08:28:13 -0600 [thread overview]
Message-ID: <3fa26fac-5317-4c09-a181-c9c15e124972@kernel.dk> (raw)
In-Reply-To: <20261029094842.58dc252d@gandalf.local.home>
On 10/29/26 7:48 AM, Steven Rostedt wrote:
> On Thu, 29 Oct 2026 07:42:09 -0600
> Jens Axboe <axboe@kernel.dk> wrote:
>
>> I don't think your analysis is fully correct. On PREEMPT_RT, spin_lock()
>> should still be an RCU read side critical section. __rt_spin_lock()
>> calls rcu_read_lock() after taking the rtmutex, and then
>> rt_spin_unlock() drops it at the end. There's even a comment on
>> kfree_rcu() callbacks in there too, it should not be able to run until
>> napi_lock is released, which is post the loop.
>
> Good point.
If even the preempt rt people can't get this right, that's a little
worrying :)
>> IOW, I think this patch is unnecessary - there's no bug there. The list
>> safe change could be done as a cleanup, but it's not a fix.
>
> I agree, it should still be applied, but as a clean up and not a fix.
Sure, like I said, as a cleanup. But would need a resend as the
analysis in the commit message is entirely wrong.
--
Jens Axboe
next prev parent reply other threads:[~2026-10-29 14:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-29 10:22 [PATCH] io_uring/napi: fix list use-after-free on PREEMPT_RT Anvik Loitongbam
2026-10-29 13:35 ` Steven Rostedt
2026-10-29 13:42 ` Jens Axboe
2026-10-29 13:48 ` Steven Rostedt
2026-10-29 14:28 ` Jens Axboe [this message]
2026-10-29 14:31 ` Steven Rostedt
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