[137/289] tty_ldisc: Fix BUG() on hangup

Greg KH
2010-12-08T01:01:32Z

From: =?UTF-8?q?Philippe=20R=C3=A9tornaz?= <philippe.retornaz@epfl.ch>

commit 1c95ba1e1de7edffc0c4e275e147f1a9eb1f81ae upstream.

A kernel BUG when bluetooth rfcomm connection drop while the associated
serial port is open is sometime triggered.

It seems that the line discipline can disappear between the
tty_ldisc_put and tty_ldisc_get. This patch fall back to the N_TTY line
discipline if the previous discipline is not available anymore.

Signed-off-by: Philippe Retornaz <philippe.retornaz@epfl.ch>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/char/tty_ldisc.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)

--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -743,9 +743,12 @@ static void tty_reset_termios(struct tty
* state closed
*/

-static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
+static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
{
- struct tty_ldisc *ld;
+ struct tty_ldisc *ld = tty_ldisc_get(ldisc);
+
+ if (IS_ERR(ld))
+ return -1;

tty_ldisc_close(tty, tty->ldisc);
tty_ldisc_put(tty->ldisc);
@@ -753,10 +756,10 @@ static void tty_ldisc_reinit(struct tty_
/*
* Switch the line discipline back
*/
- ld = tty_ldisc_get(ldisc);
- BUG_ON(IS_ERR(ld));
tty_ldisc_assign(tty, ld);
tty_set_termios_ldisc(tty, ldisc);
+
+ return 0;
}

/**
@@ -831,13 +834,16 @@ void tty_ldisc_hangup(struct tty_struct
a FIXME */
if (tty->ldisc) { /* Not yet closed */
if (reset == 0) {
- tty_ldisc_reinit(tty, tty->termios->c_line);
- err = tty_ldisc_open(tty, tty->ldisc);
+
+ if (!tty_ldisc_reinit(tty, tty->termios->c_line))
+ err = tty_ldisc_open(tty, tty->ldisc);
+ else
+ err = 1;
}
/* If the re-open fails or we reset then go to N_TTY. The
N_TTY open cannot fail */
if (reset || err) {
- tty_ldisc_reinit(tty, N_TTY);
+ BUG_ON(tty_ldisc_reinit(tty, N_TTY));
WARN_ON(tty_ldisc_open(tty, tty->ldisc));
}
tty_ldisc_enable(tty);