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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 ||
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