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Commit a570a49a authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: Handle NULL tty->ldisc 



In preparation of destroying line discipline on hangup, fix
ldisc core operations to properly handle when the tty's ldisc is
NULL.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e55afd11

drivers/tty/tty_ldisc.c

+12 −4
Original line number Diff line number Diff line
@@ -269,7 +269,8 @@ const struct file_operations tty_ldiscs_proc_fops = { 
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)

{

	ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT);

	WARN_ON(!tty->ldisc);

	if (!tty->ldisc)

		ldsem_up_read(&tty->ldisc_sem);

	return tty->ldisc;

}

EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
@@ -460,7 +461,7 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) 
		if (ret)

			clear_bit(TTY_LDISC_OPEN, &tty->flags);



		tty_ldisc_debug(tty, "%p: opened\n", tty->ldisc);

		tty_ldisc_debug(tty, "%p: opened\n", ld);

		return ret;

	}

	return 0;
@@ -481,7 +482,7 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) 
	clear_bit(TTY_LDISC_OPEN, &tty->flags);

	if (ld->ops->close)

		ld->ops->close(tty);

	tty_ldisc_debug(tty, "%p: closed\n", tty->ldisc);

	tty_ldisc_debug(tty, "%p: closed\n", ld);

}



/**
@@ -544,6 +545,11 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) 
	if (retval)

		goto err;



	if (!tty->ldisc) {

		retval = -EIO;

		goto out;

	}



	/* Check the no-op case */

	if (tty->ldisc->ops->num == ldisc)

		goto out;
@@ -659,7 +665,7 @@ void tty_ldisc_hangup(struct tty_struct *tty) 
	int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;

	int err = 0;



	tty_ldisc_debug(tty, "%p: closing\n", tty->ldisc);

	tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc);



	ld = tty_ldisc_ref(tty);

	if (ld != NULL) {
@@ -743,6 +749,8 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) 


static void tty_ldisc_kill(struct tty_struct *tty)

{

	if (!tty->ldisc)

		return;

	/*

	 * Now kill off the ldisc

	 */