From: Richard Cochran <richardcochran@gmail.com>
To: Jeongjun Park <aha310510@gmail.com>
Cc: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, yangbo.lu@nxp.com,
vladimir.oltean@nxp.com, anna-maria@linutronix.de,
frederic@kernel.org, tglx@linutronix.de, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org,
syzbot+7cfb66a237c4a5fb22ad@syzkaller.appspotmail.com
Subject: Re: [PATCH net v4] ptp: prevent possible ABBA deadlock in ptp_clock_freerun()
Date: Mon, 28 Jul 2025 07:09:51 -0700 [thread overview]
Message-ID: <aIeEr0ScB32ysLPu@hoboy.vegasvil.org> (raw)
In-Reply-To: <20250728062649.469882-1-aha310510@gmail.com>
On Mon, Jul 28, 2025 at 03:26:49PM +0900, Jeongjun Park wrote:
> However, when unregistering vclocks in n_vclocks_store(), the locking
> ptp->n_vclocks_mux is a physical clock lock, but clk->rwsem of
> ptp_clock_unregister() called through device_for_each_child_reverse()
> is a virtual clock lock.
>
> Therefore, clk->rwsem used in CPU0 and clk->rwsem used in CPU1 are
> different locks, but in lockdep, a false positive occurs because the
> possibility of deadlock is determined through lock-class.
>
> To solve this, lock subclass annotation must be added to the posix_clock
> rwsem of the vclock.
>
> Reported-by: syzbot+7cfb66a237c4a5fb22ad@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=7cfb66a237c4a5fb22ad
> Fixes: 73f37068d540 ("ptp: support ptp physical/virtual clocks conversion")
> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
next prev parent reply other threads:[~2025-07-28 14:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-28 6:26 [PATCH net v4] ptp: prevent possible ABBA deadlock in ptp_clock_freerun() Jeongjun Park
2025-07-28 14:09 ` Richard Cochran [this message]
2025-07-29 15:48 ` Vladimir Oltean
2025-08-05 23:52 ` Jakub Kicinski
2025-08-24 3:23 ` Jeongjun Park
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