The tty buffers (and any line discipline buffers) must be flushed after the UART hardware has shutdown; otherwise, a racing open on the same tty may receive data from the previous session, which is a security hazard. However, holding the port mutex while flushing the line discipline buffers creates a lock inversion if the set_termios() handler takes the port mutex (as it does in the followup patch, 'serial: Fix locking for uart driver set_termios method'.
Flush the ldisc buffers after dropping the port mutex; the tty lock is still held which prevents a concurrent open() from advancing while flushing. Since no new rx data is possible after uart_shutdown() until a new open reinitializes the port, the later flush has no impact on what data is being discarded. Signed-off-by: Peter Hurley <[email protected]> --- drivers/tty/serial/serial_core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index ce0e762..6203c6c 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1360,9 +1360,6 @@ static void uart_close(struct tty_struct *tty, struct file *filp) mutex_lock(&port->mutex); uart_shutdown(tty, state); - - tty_ldisc_flush(tty); - tty_port_tty_set(port, NULL); tty->closing = 0; spin_lock_irqsave(&port->lock, flags); @@ -1389,6 +1386,8 @@ static void uart_close(struct tty_struct *tty, struct file *filp) wake_up_interruptible(&port->close_wait); mutex_unlock(&port->mutex); + + tty_ldisc_flush(tty); } static void uart_wait_until_sent(struct tty_struct *tty, int timeout) -- 2.1.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
