linux-kernel - [PATCH 13/16] asus-wmi: Restrict debugfs interface when the kernel is locked down

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Message-ID: <147933293066.19316.11104613433360959201.stgit@warthog.procyon.org.uk>
Date:   Wed, 16 Nov 2016 21:48:50 +0000
From:   David Howells <dhowells@...hat.com>
To:     keyrings@...r.kernel.org
Cc:     dhowells@...hat.com, matthew.garrett@...ula.com,
        linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 13/16] asus-wmi: Restrict debugfs interface when the kernel
 is locked down

From: Matthew Garrett <matthew.garrett@...ula.com>

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, circumventing module loading restrictions.  Prevent that if the
kernel is locked down.

Signed-off-by: Matthew Garrett <matthew.garrett@...ula.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 drivers/platform/x86/asus-wmi.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index ce6ca31a2d09..d860017f5240 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1872,6 +1872,9 @@ static int show_dsts(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval);
 
 	if (err < 0)
@@ -1888,6 +1891,9 @@ static int show_devs(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param,
 				    &retval);
 
@@ -1912,6 +1918,9 @@ static int show_call(struct seq_file *m, void *data)
 	union acpi_object *obj;
 	acpi_status status;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID,
 				     1, asus->debug.method_id,
 				     &input, &output);