linux-kernel - [PATCH v5 4/7] serial: core: make sure RS485 cannot be enabled when it is not supported

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20231209125836.16294-5-l.sanfilippo@kunbus.com>
Date:   Sat,  9 Dec 2023 13:58:33 +0100
From:   Lino Sanfilippo <l.sanfilippo@...bus.com>
To:     gregkh@...uxfoundation.org, jirislaby@...nel.org,
        ilpo.jarvinen@...ux.intel.com
Cc:     u.kleine-koenig@...gutronix.de, shawnguo@...nel.org,
        s.hauer@...gutronix.de, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, cniedermaier@...electronics.com,
        hugo@...ovil.com, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org, LinoSanfilippo@....de,
        lukas@...ner.de, p.rosenberger@...bus.com,
        Lino Sanfilippo <l.sanfilippo@...bus.com>,
        stable@...r.kernel.org
Subject: [PATCH v5 4/7] serial: core: make sure RS485 cannot be enabled when it is not supported

Some uart drivers specify a rs485_config() function and then decide later
to disable RS485 support for some reason (e.g. imx and ar933).

In these cases userspace may be able to activate RS485 via TIOCSRS485
nevertheless, since in uart_set_rs485_config() an existing rs485_config()
function indicates that RS485 is supported.

Make sure that this is not longer possible by checking the uarts
rs485_supported.flags instead and bailing out if SER_RS485_ENABLED is not
set.

Furthermore instead of returning an empty structure return -ENOTTY if the
RS485 configuration is requested via TIOCGRS485 but RS485 is not supported.
This has a small impact on userspace visibility but it is consistent with
the -ENOTTY error for TIOCGRS485.

Fixes: e849145e1fdd ("serial: ar933x: Fill in rs485_supported")
Fixes: 55e18c6b6d42 ("serial: imx: Remove serial_rs485 sanitization")
Cc: Shawn Guo <shawnguo@...nel.org>
Cc: Sascha Hauer <s.hauer@...gutronix.de>
Cc: stable@...r.kernel.org
Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
---
 drivers/tty/serial/serial_core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 4eae1406cb6c..661074ab8edb 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1448,6 +1448,9 @@ static int uart_get_rs485_config(struct uart_port *port,
 	unsigned long flags;
 	struct serial_rs485 aux;
 
+	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
+		return -ENOTTY;
+
 	uart_port_lock_irqsave(port, &flags);
 	aux = port->rs485;
 	uart_port_unlock_irqrestore(port, flags);
@@ -1465,7 +1468,7 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
 	int ret;
 	unsigned long flags;
 
-	if (!port->rs485_config)
+	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
 		return -ENOTTY;
 
 	if (copy_from_user(&rs485, rs485_user, sizeof(*rs485_user)))
-- 
2.42.0