diff options
| author | Dmitry Safonov <dima@arista.com> | 2019-01-09 01:17:40 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-01-11 17:03:42 +0100 |
| commit | d3736d82e8169768218ee0ef68718875918091a0 (patch) | |
| tree | 0a7ee066b464a7a41104646d07a2513d95e89b76 /drivers/tty/tty_io.c | |
| parent | d3a28a53630e1ca10f59562ef560e3f70785cb09 (diff) | |
tty: Don't hold ldisc lock in tty_reopen() if ldisc present
Try to get reference for ldisc during tty_reopen().
If ldisc present, we don't need to do tty_ldisc_reinit() and lock the
write side for line discipline semaphore.
Effectively, it optimizes fast-path for tty_reopen(), but more
importantly it won't interrupt ongoing IO on the tty as no ldisc change
is needed.
Fixes user-visible issue when tty_reopen() interrupted login process for
user with a long password, observed and reported by Lukas.
Fixes: c96cf923a98d ("tty: Don't block on IO when ldisc change is pending")
Fixes: 83d817f41070 ("tty: Hold tty_ldisc_lock() during tty_reopen()")
Cc: Jiri Slaby <jslaby@suse.com>
Reported-by: Lukas F. Hartmann <lukas@mntmn.com>
Tested-by: Lukas F. Hartmann <lukas@mntmn.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_io.c')
| -rw-r--r-- | drivers/tty/tty_io.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index bfe9ad85b362..23c6fd238422 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1256,7 +1256,8 @@ static void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct * static int tty_reopen(struct tty_struct *tty) { struct tty_driver *driver = tty->driver; - int retval; + struct tty_ldisc *ld; + int retval = 0; if (driver->type == TTY_DRIVER_TYPE_PTY && driver->subtype == PTY_TYPE_MASTER) @@ -1268,13 +1269,18 @@ static int tty_reopen(struct tty_struct *tty) if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN)) return -EBUSY; - retval = tty_ldisc_lock(tty, 5 * HZ); - if (retval) - return retval; + ld = tty_ldisc_ref_wait(tty); + if (ld) { + tty_ldisc_deref(ld); + } else { + retval = tty_ldisc_lock(tty, 5 * HZ); + if (retval) + return retval; - if (!tty->ldisc) - retval = tty_ldisc_reinit(tty, tty->termios.c_line); - tty_ldisc_unlock(tty); + if (!tty->ldisc) + retval = tty_ldisc_reinit(tty, tty->termios.c_line); + tty_ldisc_unlock(tty); + } if (retval == 0) tty->count++; |