diff options
| author |   Peter Hurley <peter@hurleysoftware.com> | 2014-10-16 16:54:20 -0400 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-11-05 18:53:54 -0800 |
| commit | 7c8ab967e3cd1513cd79fd5edc404fb43c7f3a96 (patch) | |
| tree | 2fadec4ea6f6d183b2b6e5b81453a57b8670e390 /drivers/tty/serial/serial_core.c | |
| parent | serial: core: Flush ldisc after dropping port mutex in uart_close() (diff) | |
| download | linux-dev-7c8ab967e3cd1513cd79fd5edc404fb43c7f3a96.tar.xz linux-dev-7c8ab967e3cd1513cd79fd5edc404fb43c7f3a96.zip | |
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.c | 8 |
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; |