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>
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index ad9120d..62380cc 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -1164,17 +1164,21 @@
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)