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Commit 1c95ba1e authored by Philippe Rétornaz's avatar Philippe Rétornaz Committed by Greg Kroah-Hartman
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tty_ldisc: Fix BUG() on hangup 



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: default avatarPhilippe Retornaz <philippe.retornaz@epfl.ch>
Acked-by: default avatarAlan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 100eeae2

drivers/tty/tty_ldisc.c

+13 −7
Original line number Diff line number Diff line
@@ -743,9 +743,12 @@ static void tty_reset_termios(struct tty_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_struct *tty, int ldisc) 
	/*

	 *	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 *tty) 
	   a FIXME */

	if (tty->ldisc) {	/* Not yet closed */

		if (reset == 0) {

			tty_ldisc_reinit(tty, tty->termios->c_line);



			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);