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Subject[PATCH 23/24] Lock down TIOCSSERIAL
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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 3fe56894974a..4181b0004de9 100644
--- 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 ||
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