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    Subject[PATCH 21/30] Lock down TIOCSSERIAL
    Date
    Lock down TIOCSSERIAL as that can be used to change the ioport and irq
    settings on a serial port. This only appears to be an issue for the serial
    drivers that use the core serial code. All other drivers seem to either
    ignore attempts to change port/irq or give an error.

    Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: David Howells <dhowells@redhat.com>
    cc: Jiri Slaby <jslaby@suse.com>
    ---

    drivers/tty/serial/serial_core.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
    index 3a14cccbd7ff..41f0922ad842 100644
    --- a/drivers/tty/serial/serial_core.c
    +++ b/drivers/tty/serial/serial_core.c
    @@ -842,6 +842,12 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
    new_flags = (__force upf_t)new_info->flags;
    old_custom_divisor = uport->custom_divisor;

    + if ((change_port || change_irq) &&
    + kernel_is_locked_down("Using TIOCSSERIAL to change device addresses, irqs and dma channels")) {
    + retval = -EPERM;
    + goto exit;
    + }
    +
    if (!capable(CAP_SYS_ADMIN)) {
    retval = -EPERM;
    if (change_irq || change_port ||
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