Lock down TIOCSSERIAL

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>
Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0060-Lock-down-TIOCSSERIAL.patch

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 13bfd5dcffce5c0bfaee47879277e32aedf308a9..45fb7689bc1c8897f55b2c75c29ba4258762eaee 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -821,6 +821,12 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
        new_flags = new_info->flags;
        old_custom_divisor = uport->custom_divisor;
 
+       if ((change_port || change_irq) && kernel_is_locked_down()) {
+               pr_err("Using TIOCSSERIAL to change device addresses, irqs and dma channels is not permitted when the kernel is locked down\n");
+               retval = -EPERM;
+               goto exit;
+       }
+
        if (!capable(CAP_SYS_ADMIN)) {
                retval = -EPERM;
                if (change_irq || change_port ||