Patch "serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485)" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
serial-omap-prevent-dos-using-unprivileged-ioctl-tiocsrs485.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Peter Hurley <[email protected]>
Date: Tue, 12 Jan 2016 15:14:46 -0800
Subject: serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485)

From: Peter Hurley <[email protected]>

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.

---
 drivers/tty/serial/omap-serial.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

@@ -1343,7 +1343,7 @@ static inline void serial_omap_add_conso
 
 /* 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;

@@ -1356,8 +1356,12 @@ serial_omap_config_rs485(struct uart_por
 	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

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/staging-speakup-use-tty_ldisc_ref-for-paste-kworker.patch queue-4.4/pty-make-sure-super_block-is-still-valid-in-final-dev-tty-close.patch queue-4.4/serial-omap-prevent-dos-using-unprivileged-ioctl-tiocsrs485.patch queue-4.4/pty-fix-possible-use-after-free-of-tty-driver_data.patch