From: David Howells <dhowells@redhat.com> Date: Wed, 8 Nov 2017 15:11:35 +0000 Subject: [21/29] Lock down TIOCSSERIAL Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=f5fdeda0622ca040961521819794193777a03e8a 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(+) Index: linux/drivers/tty/serial/serial_core.c =================================================================== --- linux.orig/drivers/tty/serial/serial_core.c +++ linux/drivers/tty/serial/serial_core.c @@ -850,6 +850,12 @@ static int uart_set_info(struct tty_stru 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 ||