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[4.2.y-ckt,stable] Patch "serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485)" has been added to the 4.2.y-ckt tree

Message ID 1457389989-29829-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa March 7, 2016, 10:33 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485)

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt5.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

From f55f3ed6e60f0bfe7f4c13c60254040cde49faa8 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Tue, 12 Jan 2016 15:14:46 -0800
Subject: serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485)

commit 308bbc9ab838d0ace0298268c7970ba9513e2c65 upstream.

The omap-serial driver emulates RS485 delays using software timers,
but neglects to clamp the input values from the unprivileged
ioctl(TIOCSRS485). Because the software implementation busy-waits,
malicious userspace could stall the cpu for ~49 days.

Clamp the input values to < 100ms.

Fixes: 4a0ac0f55b18 ("OMAP: add RS485 support")
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/tty/serial/omap-serial.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--
2.7.0
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Patch

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 7a2172b..aaf3478 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1341,7 +1341,7 @@  static inline void serial_omap_add_console_port(struct uart_omap_port *up)

 /* Enable or disable the rs485 support */
 static int
-serial_omap_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf)
+serial_omap_config_rs485(struct uart_port *port, struct serial_rs485 *rs485)
 {
 	struct uart_omap_port *up = to_uart_omap_port(port);
 	unsigned int mode;
@@ -1354,8 +1354,12 @@  serial_omap_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf)
 	up->ier = 0;
 	serial_out(up, UART_IER, 0);

+	/* Clamp the delays to [0, 100ms] */
+	rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
+	rs485->delay_rts_after_send  = min(rs485->delay_rts_after_send, 100U);
+
 	/* store new config */
-	port->rs485 = *rs485conf;
+	port->rs485 = *rs485;

 	/*
 	 * Just as a precaution, only allow rs485