[PATCH 14/16] tty: mxser: fix TIOCSSERIAL permission check

Johan Hovold
2021-04-07T10:24:35Z

Changing the port type and closing_wait parameter are privileged
operations so make sure to return -EPERM if a regular user tries to
change them.

Note that the closing_wait parameter would not actually have been
changed but the return value did not indicate that.

Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/tty/mxser.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 914b23071961..2d8e76263a25 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -1270,6 +1270,7 @@ static int mxser_set_serial_info(struct tty_struct *tty,
if (!capable(CAP_SYS_ADMIN)) {
if ((ss->baud_base != info->baud_base) ||
(close_delay != info->port.close_delay) ||
+ (closing_wait != info->port.closing_wait) ||
((ss->flags & ~ASYNC_USR_MASK) != (info->port.flags & ~ASYNC_USR_MASK))) {
mutex_unlock(&port->mutex);
return -EPERM;
@@ -1296,11 +1297,11 @@ static int mxser_set_serial_info(struct tty_struct *tty,
baud = ss->baud_base / ss->custom_divisor;
tty_encode_baud_rate(tty, baud, baud);
}
- }

- info->type = ss->type;
+ info->type = ss->type;

- process_txrx_fifo(info);
+ process_txrx_fifo(info);
+ }

if (tty_port_initialized(port)) {
if (flags != (port->flags & ASYNC_SPD_MASK)) {
--
2.26.3