netdev - Re: [PATCH net] mISDN: Fix data race in timer handling

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Message-ID: <CACkPEmnTuQ-FpVtydxuXEeocV2QMxZyjJPE1TDck-nte462ZuA@mail.gmail.com>
Date: Wed, 28 Jan 2026 14:00:54 -0500
From: Henry Zhang <zeri@...ch.edu>
To: Simon Horman <horms@...nel.org>
Cc: Henry Zhang <henryzhangjcle@...il.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...nel.org, 
	syzbot+c6e7bcea7ffb7ff46acb@...kaller.appspotmail.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net] mISDN: Fix data race in timer handling

On Wed, Jan 28, 2026 at 12:37 PM Simon Horman <horms@...nel.org> wrote:
>
> + Eric
>
> On Tue, Jan 27, 2026 at 02:19:27AM -0500, Henry Zhang wrote:
> > KCSAN reported a data race where misdn_add_timer() writes dev->work
> > while mISDN_read() reads it without holding the spinlock:
> >
> > write to 0xffff88812d848280 of 4 bytes by task 10864 on cpu 1:
> >  misdn_add_timer drivers/isdn/mISDN/timerdev.c:175 [inline]
> > ...
> >
> > read to 0xffff88812d848280 of 4 bytes by task 10857 on cpu 0:
> >  mISDN_read+0x1f2/0x470 drivers/isdn/mISDN/timerdev.c:112
> > ...
> >
> > dev->work is read locklessly in wait_event_interruptible() and
> > mISDN_poll(). In mISDN_read(), the result is rechecked under dev->lock.
> > In mISDN_poll(), a stale value may cause a spurious EPOLLIN or a missed
> > wake, but wake_up_interruptible() will correct this. In both cases, the
> > race is benign, so we can annotate these with READ_ONCE/WRITE_ONCE.
> >
> > Reported-by: syzbot+c6e7bcea7ffb7ff46acb@...kaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=c6e7bcea7ffb7ff46acb
> >
> > Signed-off-by: Henry Zhang <zeri@...ch.edu>
>
> Hi Henry,
>
> This appears to already be addressed by
> commit 8175dbf174d4 ("mISDN: annotate data-race around dev->work")
>
> --
> pw-bot: cr
Hi Simon,

Thanks for pointing this out. Dropping this patch.

Henry