linux-kernel - [PATCH 11/12] asus-wmi: Restrict debugfs interface when trusted

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Date:	Fri, 13 Mar 2015 11:38:27 -1000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	linux-security-module@...r.kernel.org
Cc:	james.l.morris@...cle.com, serge@...lyn.com,
	linux-kernel@...r.kernel.org, keescook@...omium.org, hpa@...or.com,
	gnomes@...rguk.ukuu.org.uk,
	Matthew Garrett <matthew.garrett@...ula.com>
Subject: [PATCH 11/12] asus-wmi: Restrict debugfs interface when trusted_kernel is true

We have no way of validating what all of the Asus WMI methods do on a
given machine, and there's a risk that some will allow hardware state to
be manipulated in such a way that arbitrary code can be executed in the
kernel. Prevent that if trusted_kernel is true.

Signed-off-by: Matthew Garrett <matthew.garrett@...ula.com>
---
 drivers/platform/x86/asus-wmi.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 7543a56..d708fdc 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -47,6 +47,7 @@
 #include <linux/thermal.h>
 #include <linux/acpi.h>
 #include <linux/dmi.h>
+#include <linux/security.h>
 #include <acpi/video.h>
 
 #include "asus-wmi.h"
@@ -1589,6 +1590,9 @@ static int show_dsts(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (get_trusted_kernel())
+		return -EPERM;
+
 	err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval);
 
 	if (err < 0)
@@ -1605,6 +1609,9 @@ static int show_devs(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (get_trusted_kernel())
+		return -EPERM;
+
 	err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param,
 				    &retval);
 
@@ -1629,6 +1636,9 @@ static int show_call(struct seq_file *m, void *data)
 	union acpi_object *obj;
 	acpi_status status;
 
+	if (get_trusted_kernel())
+		return -EPERM;
+
 	status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID,
 				     1, asus->debug.method_id,
 				     &input, &output);
-- 
2.1.0

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