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    Subject[PATCH 3.16.y-ckt 103/129] serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485)
    Date
    3.16.7-ckt25 -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>
    [ luis: backported to 3.16: adjusted context ]
    Signed-off-by: Luis Henriques <luis.henriques@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 e454b7c2ecd9..9053aa7a970f 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
    \
     
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