linux-kernel - [PATCH 5.11 243/601] staging: greybus: uart: fix unprivileged TIOCCSERIAL

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Date:   Wed, 12 May 2021 16:45:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 243/601] staging: greybus: uart: fix unprivileged TIOCCSERIAL

From: Johan Hovold <johan@...nel.org>

[ Upstream commit 60c6b305c11b5fd167ce5e2ce42f3a9098c388f0 ]

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 greybus implementation which instead indicated that the
TIOCSSERIAL ioctl was not even implemented when a non-privileged user
set the current values.

Fixes: e68453ed28c5 ("greybus: uart-gb: now builds, more framework added")
Signed-off-by: Johan Hovold <johan@...nel.org>
Link: https://lore.kernel.org/r/20210407102334.32361-7-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/staging/greybus/uart.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c
index 29846dc1e1bf..a520f7f213db 100644
--- a/drivers/staging/greybus/uart.c
+++ b/drivers/staging/greybus/uart.c
@@ -641,8 +641,6 @@ static int set_serial_info(struct tty_struct *tty,
 		if ((close_delay != gb_tty->port.close_delay) ||
 		    (closing_wait != gb_tty->port.closing_wait))
 			retval = -EPERM;
-		else
-			retval = -EOPNOTSUPP;
 	} else {
 		gb_tty->port.close_delay = close_delay;
 		gb_tty->port.closing_wait = closing_wait;
-- 
2.30.2