[PATCH] tty: Fix data race between tiocsti() and flush_to_ldisc()
phind.uet at gmail.com
Fri Aug 13 18:35:53 UTC 2021
On 8/13/2021 3:33 PM, Greg KH wrote:
>> Signed-off-by: Nguyen Dinh Phi <phind.uet at gmail.com>
>> Reported-by: syzbot+97388eb9d31b997fe1d0 at syzkaller.appspotmail.com
>> drivers/tty/tty_io.c | 2 ++
>> 1 file changed, 2 insertions(+)
>> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
>> index e8532006e960..746fe13a2054 100644
>> --- a/drivers/tty/tty_io.c
>> +++ b/drivers/tty/tty_io.c
>> @@ -2307,8 +2307,10 @@ static int tiocsti(struct tty_struct *tty, char __user *p)
>> ld = tty_ldisc_ref_wait(tty);
>> if (!ld)
>> return -EIO;
>> + tty_buffer_lock_exclusive(tty->port);
>> if (ld->ops->receive_buf)
>> ld->ops->receive_buf(tty, &ch, &mbz, 1);
>> + tty_buffer_unlock_exclusive(tty->port);
> Did this fix the syzbot reported issue?
> greg k-h
> Yes, this fixed the syzbot reported issue.
The lock is grabbed in flush_to_ldisc() and paste_selection().
Actually, I follow the document in tty_buffer.c, where it say the
callers to receive_buff() other than flush_to_ldisc() need to exclude
the kworker from concurrent use of the line discipline.
And function tiocsti() has the following comment:
/* FIXME: may race normal receive processing */
that why I add lock in this function.
More information about the Linux-kernel-mentees