Messages in this thread Patch in this message | | | From | Kamal Mostafa <> | Subject | [PATCH 4.2.y-ckt 117/273] serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485) | Date | Mon, 7 Mar 2016 14:48:28 -0800 |
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4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Peter Hurley <peter@hurleysoftware.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@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(-)
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 -- 2.7.0
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