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Commit c274f6ef authored Sep 10, 2014 by Peter Hurley Committed by Greg Kroah-Hartman Sep 23, 2014

tty: Hold termios_rwsem for tcflow(TCIxxx)

While transmitting a START/STOP char for tcflow(TCION/TCIOFF), prevent
a termios change. Otherwise, a garbage in-band flow control char
may be sent, if the termios change overlaps the transmission setup.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 136d5258

drivers/tty/tty_ioctl.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -1164,17 +1164,21 @@ int n_tty_ioctl_helper(struct tty_struct tty, struct file file,
		spin_unlock_irq(&tty->flow_lock);
		break;
		case TCIOFF:
		down_read(&tty->termios_rwsem);
		if (STOP_CHAR(tty) != __DISABLED_CHAR)
		return tty_send_xchar(tty, STOP_CHAR(tty));
		retval = tty_send_xchar(tty, STOP_CHAR(tty));
		up_read(&tty->termios_rwsem);
		break;
		case TCION:
		down_read(&tty->termios_rwsem);
		if (START_CHAR(tty) != __DISABLED_CHAR)
		return tty_send_xchar(tty, START_CHAR(tty));
		retval = tty_send_xchar(tty, START_CHAR(tty));
		up_read(&tty->termios_rwsem);
		break;
		default:
		return -EINVAL;
		}
		return 0;
		return retval;
		case TCFLSH:
		retval = tty_check_change(tty);
		if (retval)