From: David Howells <dhowells@redhat.com>
Date: Mon, 19 Aug 2019 17:17:54 -0700
Subject: lockdown: Lock down TIOCSSERIAL
Patch-mainline: v5.4-rc1
Git-commit: 794edf30ee6cd088d5f4079b1d4a4cfe5371203e
References: jsc#SLE-9870
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>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-serial@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
drivers/tty/serial/serial_core.c | 5 +++++
include/linux/security.h | 1 +
security/lockdown/lockdown.c | 1 +
3 files changed, 7 insertions(+)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -22,6 +22,7 @@
#include <linux/serial_core.h>
#include <linux/delay.h>
#include <linux/mutex.h>
+#include <linux/security.h>
#include <linux/irq.h>
#include <linux/uaccess.h>
@@ -862,6 +863,10 @@ static int uart_set_info(struct tty_stru
goto check_and_exit;
}
+ retval = security_locked_down(LOCKDOWN_TIOCSSERIAL);
+ if (retval && (change_irq || change_port))
+ goto exit;
+
/*
* Ask the low level driver to verify the settings.
*/
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -112,6 +112,7 @@ enum lockdown_reason {
LOCKDOWN_MSR,
LOCKDOWN_ACPI_TABLES,
LOCKDOWN_PCMCIA_CIS,
+ LOCKDOWN_TIOCSSERIAL,
LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_CONFIDENTIALITY_MAX,
};
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -27,6 +27,7 @@ static char *lockdown_reasons[LOCKDOWN_C
[LOCKDOWN_MSR] = "raw MSR access",
[LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables",
[LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage",
+ [LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO",
[LOCKDOWN_INTEGRITY_MAX] = "integrity",
[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
};