linux-kernel - [PATCH 12/16] tty: moxa: fix TIOCSSERIAL implementation

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Date:   Wed,  7 Apr 2021 12:23:30 +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>
Subject: [PATCH 12/16] tty: moxa: fix TIOCSSERIAL implementation

TIOCSSERIAL is a horrid, underspecified, legacy interface which for most
serial devices is only useful for setting the close_delay and
closing_wait parameters.

A non-privileged user has only ever been able to set the since long
deprecated ASYNC_SPD flags and trying to change any other *supported*
feature should result in -EPERM being returned. Setting the current
values for any supported features should return success.

Fix the moxa implementation which was returning -EPERM also for a
privileged user when trying to change certain unsupported parameters and
instead return success consistently.

Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/tty/moxa.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/tty/moxa.c b/drivers/tty/moxa.c
index 63e440d900ff..4d4f15b5cd29 100644
--- a/drivers/tty/moxa.c
+++ b/drivers/tty/moxa.c
@@ -2055,11 +2055,6 @@ static int moxa_set_serial_info(struct tty_struct *tty,
 	if (!info)
 		return -ENODEV;

-	if (ss->irq != 0 || ss->port != 0 ||
-			ss->custom_divisor != 0 ||
-			ss->baud_base != 921600)
-		return -EPERM;
-
 	close_delay = msecs_to_jiffies(ss->close_delay * 10);

 	mutex_lock(&info->port.mutex);
-- 
2.26.3