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Date: Wed, 9 Mar 2016 15:13:09 -0800 From: Kamal Mostafa <kamal@...onical.com> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, kernel-team@...ts.ubuntu.com Cc: Peter Hurley <peter@...leysoftware.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Luis Henriques <luis.henriques@...onical.com>, Kamal Mostafa <kamal@...onical.com> Subject: [PATCH 3.13.y-ckt 062/138] serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485) 3.13.11-ckt36 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Peter Hurley <peter@...leysoftware.com> 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@...leysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> [ luis: backported to 3.16: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@...onical.com> Signed-off-by: Kamal Mostafa <kamal@...onical.com> --- drivers/tty/serial/omap-serial.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c index 270d084..dabf668 100644 --- a/drivers/tty/serial/omap-serial.c +++ b/drivers/tty/serial/omap-serial.c @@ -1365,7 +1365,7 @@ 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; @@ -1380,8 +1380,12 @@ 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 -- 2.7.0
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