diff options
| author | Dmitry Safonov <dima@arista.com> | 2018-11-01 03:24:47 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-12-05 14:16:33 +0300 |
| commit | 83d817f41070c48bc3eb7ec18e43000a548fca5c (patch) | |
| tree | c8c2a72074c45fabce2963529533d8c33fc87537 | |
| parent | 231f8fd0cca078bd4396dd7e380db813ac5736e2 (diff) | |
| download | linux-83d817f41070c48bc3eb7ec18e43000a548fca5c.tar.xz | |
tty: Hold tty_ldisc_lock() during tty_reopen()
tty_ldisc_reinit() doesn't race with neither tty_ldisc_hangup()
nor set_ldisc() nor tty_ldisc_release() as they use tty lock.
But it races with anyone who expects line discipline to be the same
after hoding read semaphore in tty_ldisc_ref().
We've seen the following crash on v4.9.108 stable:
BUG: unable to handle kernel paging request at 0000000000002260
IP: [..] n_tty_receive_buf_common+0x5f/0x86d
Workqueue: events_unbound flush_to_ldisc
Call Trace:
[..] n_tty_receive_buf2
[..] tty_ldisc_receive_buf
[..] flush_to_ldisc
[..] process_one_work
[..] worker_thread
[..] kthread
[..] ret_from_fork
tty_ldisc_reinit() should be called with ldisc_sem hold for writing,
which will protect any reader against line discipline changes.
Cc: Jiri Slaby <jslaby@suse.com>
Cc: stable@vger.kernel.org # b027e2298bd5 ("tty: fix data race between tty_init_dev and flush of buf")
Reviewed-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: syzbot+3aa9784721dfb90e984d@syzkaller.appspotmail.com
Tested-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Tested-by: Tycho Andersen <tycho@tycho.ws>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_io.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index ee80dfbd5442..f73d8fa7f02b 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1268,15 +1268,20 @@ static int tty_reopen(struct tty_struct *tty) if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN)) return -EBUSY; - tty->count++; + retval = tty_ldisc_lock(tty, 5 * HZ); + if (retval) + return retval; + tty->count++; if (tty->ldisc) - return 0; + goto out_unlock; retval = tty_ldisc_reinit(tty, tty->termios.c_line); if (retval) tty->count--; +out_unlock: + tty_ldisc_unlock(tty); return retval; } |