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tty: fix close/hangup race 

We can get a situation where a hangup occurs during or after a close. In
that case the ldisc gets disposed of by the close and the hangup then
explodes.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Cox 2009-07-16 16:05:08 +01:00 committed by Linus Torvalds
parent a3ca86aea5
commit c8d5004173
1 changed files with 15 additions and 10 deletions
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25
drivers/char/tty_ldisc.c
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@ -790,17 +790,20 @@ void tty_ldisc_hangup(struct tty_struct *tty)
* N_TTY.
*/
if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
/* Avoid racing set_ldisc */
/* Avoid racing set_ldisc or tty_ldisc_release */
mutex_lock(&tty->ldisc_mutex);
/* Switch back to N_TTY */
tty_ldisc_halt(tty);
tty_ldisc_wait_idle(tty);
tty_ldisc_reinit(tty);
/* At this point we have a closed ldisc and we want to
reopen it. We could defer this to the next open but
it means auditing a lot of other paths so this is a FIXME */
WARN_ON(tty_ldisc_open(tty, tty->ldisc));
tty_ldisc_enable(tty);
if (tty->ldisc) { /* Not yet closed */
/* Switch back to N_TTY */
tty_ldisc_halt(tty);
tty_ldisc_wait_idle(tty);
tty_ldisc_reinit(tty);
/* At this point we have a closed ldisc and we want to
reopen it. We could defer this to the next open but
it means auditing a lot of other paths so this is
a FIXME */
WARN_ON(tty_ldisc_open(tty, tty->ldisc));
tty_ldisc_enable(tty);
}
mutex_unlock(&tty->ldisc_mutex);
tty_reset_termios(tty);
}
@ -865,6 +868,7 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
tty_ldisc_wait_idle(tty);
mutex_lock(&tty->ldisc_mutex);
/*
* Now kill off the ldisc
*/
@ -875,6 +879,7 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
/* Ensure the next open requests the N_TTY ldisc */
tty_set_termios_ldisc(tty, N_TTY);
mutex_unlock(&tty->ldisc_mutex);
/* This will need doing differently if we need to lock */
if (o_tty)