From: Peter Hurley Date: Tue, 12 Jan 2016 23:14:46 +0000 (-0800) Subject: serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485) X-Git-Tag: v3.16.35~406 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=546e99d81f7b365d25ae61318d9113a26bef806f;p=thirdparty%2Fkernel%2Fstable.git 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 Signed-off-by: Greg Kroah-Hartman [ luis: backported to 3.16: adjusted context ] Signed-off-by: Luis Henriques --- diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c index e454b7c2ecd9f..9053aa7a970f1 100644 --- a/drivers/tty/serial/omap-serial.c +++ b/drivers/tty/serial/omap-serial.c @@ -1350,7 +1350,7 @@ static inline void serial_omap_add_console_port(struct uart_omap_port *up) /* Enable or disable the rs485 support */ static void -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 long flags; @@ -1365,8 +1365,12 @@ 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 */ - up->rs485 = *rs485conf; + up->rs485 = *rs485; /* * Just as a precaution, only allow rs485