summaryrefslogtreecommitdiff
path: root/drivers/tty/serial/serial_core.c
diff options
context:
space:
mode:
authorPeter Hurley <peter@hurleysoftware.com>2014-10-16 16:54:20 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-11-05 18:53:54 -0800
commit7c8ab967e3cd1513cd79fd5edc404fb43c7f3a96 (patch)
tree2fadec4ea6f6d183b2b6e5b81453a57b8670e390 /drivers/tty/serial/serial_core.c
parent2e758910832dce99761a29688b33fd77dcbf6f6c (diff)
serial: Fix locking for uart driver set_termios() method
The low-level uart driver may modify termios settings to override settings that are not compatible with the uart, such as CRTSCTS. Thus, callers of the low-level uart driver's set_termios() method must hold termios_rwsem write lock to prevent concurrent access to termios, in case such override occurs. The termios_rwsem lock requirement does not extend to console setup (ie., uart_set_options), as console setup cannot race with tty operations. Nor does this lock requirement extend to functions which cannot be concurrent with tty ioctls (ie., uart_port_startup() and uart_resume_port()). Further, always claim the port mutex to protect hardware re-reprogramming in the set_termios() uart driver method. Note this is unnecessary for console initialization in uart_set_options() which cannot be concurrent with other uart operations. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial/serial_core.c')
-rw-r--r--drivers/tty/serial/serial_core.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 9d142972ee2d..e31d56159aee 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -436,7 +436,7 @@ uart_get_divisor(struct uart_port *port, unsigned int baud)
EXPORT_SYMBOL(uart_get_divisor);
-/* FIXME: Consistent locking policy */
+/* Caller holds port mutex */
static void uart_change_speed(struct tty_struct *tty, struct uart_state *state,
struct ktermios *old_termios)
{
@@ -1173,11 +1173,15 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd,
break;
case TIOCSSERIAL:
+ down_write(&tty->termios_rwsem);
ret = uart_set_info_user(tty, state, uarg);
+ up_write(&tty->termios_rwsem);
break;
case TIOCSERCONFIG:
+ down_write(&tty->termios_rwsem);
ret = uart_do_autoconfig(tty, state);
+ up_write(&tty->termios_rwsem);
break;
case TIOCSERGWILD: /* obsolete */
@@ -1278,7 +1282,9 @@ static void uart_set_termios(struct tty_struct *tty,
return;
}
+ mutex_lock(&state->port.mutex);
uart_change_speed(tty, state, old_termios);
+ mutex_unlock(&state->port.mutex);
/* reload cflag from termios; port driver may have overriden flags */
cflag = tty->termios.c_cflag;