From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757360Ab0LHBBc (ORCPT ); Tue, 7 Dec 2010 20:01:32 -0500 Received: from kroah.org ([198.145.64.141]:49014 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757339Ab0LHBB3 (ORCPT ); Tue, 7 Dec 2010 20:01:29 -0500 X-Mailbox-Line: From gregkh@clark.site Tue Dec 7 16:57:35 2010 Message-Id: <20101208005735.086957862@clark.site> User-Agent: quilt/0.48-11.2 Date: Tue, 07 Dec 2010 16:58:34 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Philippe Retornaz , Alan Cox Subject: [137/289] tty_ldisc: Fix BUG() on hangup In-Reply-To: <20101208005821.GA2922@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.36-stable review patch. If anyone has any objections, please let us know. ------------------ From: =?UTF-8?q?Philippe=20R=C3=A9tornaz?= 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 Acked-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- 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);