The COMEDI_DEVCONFIG ioctl can be used to configure I/O addresses and
other hardware settings for non plug-and-play devices such as ISA
cards.  This should be disabled to preserve the kernel's integrity
when it is locked down.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Matthew Garrett <mjg59@google.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
---
 drivers/staging/comedi/comedi_fops.c | 6 ++++++
 include/linux/security.h             | 1 +
 security/lockdown/lockdown.c         | 1 +
 3 files changed, 8 insertions(+)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index f6d1287c7b83..fdf030e53035 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -27,6 +27,7 @@
 
 #include <linux/io.h>
 #include <linux/uaccess.h>
+#include <linux/security.h>
 
 #include "comedi_internal.h"
 
@@ -813,11 +814,16 @@ static int do_devconfig_ioctl(struct comedi_device *dev,
 			      struct comedi_devconfig __user *arg)
 {
 	struct comedi_devconfig it;
+	int ret;
 
 	lockdep_assert_held(&dev->mutex);
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	ret = security_locked_down(LOCKDOWN_COMEDI_DEVCONFIG);
+	if (ret)
+		return ret;
+
 	if (!arg) {
 		if (is_device_busy(dev))
 			return -EBUSY;
diff --git a/include/linux/security.h b/include/linux/security.h
index 429f9f03372b..b16365dccfc5 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -113,6 +113,7 @@ enum lockdown_reason {
 	LOCKDOWN_ACPI_TABLES,
 	LOCKDOWN_PCMCIA_CIS,
 	LOCKDOWN_TIOCSSERIAL,
+	LOCKDOWN_COMEDI_DEVCONFIG,
 	LOCKDOWN_MODULE_PARAMETERS,
 	LOCKDOWN_MMIOTRACE,
 	LOCKDOWN_DEBUGFS,
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 0068cec77c05..971bb99b9051 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -28,6 +28,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
 	[LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables",
 	[LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage",
 	[LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO",
+	[LOCKDOWN_COMEDI_DEVCONFIG] = "reconfiguration of Comedi legacy device",
 	[LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters",
 	[LOCKDOWN_MMIOTRACE] = "unsafe mmio",
 	[LOCKDOWN_DEBUGFS] = "debugfs access",