Commit 8c985d18 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

n_tty: Fix unsafe driver-side signals 



An ldisc reference is insufficient guarantee the foreground process
group is not in the process of being signalled from a hangup.

1) Reads of tty->pgrp must be locked with ctrl_lock
2) The group pid must be referenced for the duration of signalling.
   Because the driver-side is not process-context, a pid reference
   must be acquired.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e91e52e4

drivers/tty/n_tty.c

+14 −20
Original line number Diff line number Diff line
@@ -1017,23 +1017,19 @@ static void eraser(unsigned char c, struct tty_struct *tty) 
 *	isig		-	handle the ISIG optio

 *	@sig: signal

 *	@tty: terminal

 *	@flush: force flush

 *

 *	Called when a signal is being sent due to terminal input. This

 *	may caus terminal flushing to take place according to the termios

 *	settings and character used. Called from the driver receive_buf

 *	path so serialized.

 *	Called when a signal is being sent due to terminal input.

 *	Called from the driver receive_buf path so serialized.

 *

 *	Locking: ctrl_lock, read_lock (both via flush buffer)

 *	Locking: ctrl_lock

 */



static inline void isig(int sig, struct tty_struct *tty, int flush)

static inline void isig(int sig, struct tty_struct *tty)

{

	if (tty->pgrp)

		kill_pgrp(tty->pgrp, sig, 1);

	if (flush || !L_NOFLSH(tty)) {

		n_tty_flush_buffer(tty);

		tty_driver_flush_buffer(tty);

	struct pid *tty_pgrp = tty_get_pgrp(tty);

	if (tty_pgrp) {

		kill_pgrp(tty_pgrp, sig, 1);

		put_pid(tty_pgrp);

	}

}
@@ -1054,7 +1050,11 @@ static inline void n_tty_receive_break(struct tty_struct *tty) 
	if (I_IGNBRK(tty))

		return;

	if (I_BRKINT(tty)) {

		isig(SIGINT, tty, 1);

		isig(SIGINT, tty);

		if (!L_NOFLSH(tty)) {

			n_tty_flush_buffer(tty);

			tty_driver_flush_buffer(tty);

		}

		return;

	}

	if (I_PARMRK(tty)) {
@@ -1221,11 +1221,6 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) 
		signal = SIGTSTP;

		if (c == SUSP_CHAR(tty)) {

send_signal:

			/*

			 * Note that we do not use isig() here because we want

			 * the order to be:

			 * 1) flush, 2) echo, 3) signal

			 */

			if (!L_NOFLSH(tty)) {

				n_tty_flush_buffer(tty);

				tty_driver_flush_buffer(tty);
@@ -1236,8 +1231,7 @@ send_signal: 
				echo_char(c, tty);

				process_echoes(tty);

			}

			if (tty->pgrp)

				kill_pgrp(tty->pgrp, signal, 1);

			isig(signal, tty);

			return;

		}

	}

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