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

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Date:   Wed,  7 Apr 2021 12:23:32 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jirislaby@...nel.org>, linux-staging@...ts.linux.dev,
        greybus-dev@...ts.linaro.org, linux-kernel@...r.kernel.org,
        Johan Hovold <johan@...nel.org>, stable@...r.kernel.org
Subject: [PATCH 14/16] tty: mxser: fix TIOCSSERIAL permission check

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@...r.kernel.org
Signed-off-by: Johan Hovold <johan@...nel.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