[PATCH 4.4 017/137] serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2016-02-24 04:40:38
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4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Peter Hurley <redacted>
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 <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/serial/omap-serial.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c@@ -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