tty_ldisc: Fix BUG() on hangup

commit 1c95ba1 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 <[email protected]> Acked-by: Alan Cox <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> Signed-off-by: Andi Kleen <[email protected]>
GalaxySII · Dec 14, 2010 · d509e24 · d509e24
1 parent 7a4239f
commit d509e24
Showing 1 changed file with 13 additions and 7 deletions.
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
@@ -741,20 +741,23 @@ 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);
 	tty->ldisc = NULL;
 	/*
 	 *	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;
 }
 
 /**
@@ -816,13 +819,16 @@ 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);
-			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);