From c274f6ef1c6665632767d32e4ab912aad839ce27 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Wed, 10 Sep 2014 15:06:35 -0400 Subject: [PATCH] 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 Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_ioctl.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c index ad9120d1c0f1..62380ccf70fb 100644 --- a/drivers/tty/tty_ioctl.c +++ b/drivers/tty/tty_ioctl.c @@ -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) -- 2.20.1