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

[Henry Zhang]

On Wed, Jan 28, 2026 at 12:37 PM Simon Horman <horms@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://syzkaller.appspot.com/bug?extid=c6e7bcea7ffb7ff46acb
> >
> > Signed-off-by: Henry Zhang <zeri@xxxxxxxxx>
>
> 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