linux-kernel - [PATCH V2 04/10] ACPI: Limit access to custom

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Message-Id: <1376933171-9854-5-git-send-email-matthew.garrett@nebula.com>
Date:	Mon, 19 Aug 2013 13:26:05 -0400
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-efi@...r.kernel.org, jwboyer@...hat.com,
	keescook@...omium.org, Matthew Garrett <matthew.garrett@...ula.com>
Subject: [PATCH V2 04/10] ACPI: Limit access to custom_method

custom_method effectively allows arbitrary access to system memory, making
it possible for an attacker to circumvent restrictions on module loading.
Disable it if any such restrictions have been enabled.

Signed-off-by: Matthew Garrett <matthew.garrett@...ula.com>
---
 drivers/acpi/custom_method.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
index 12b62f2..55a013f 100644
--- a/drivers/acpi/custom_method.c
+++ b/drivers/acpi/custom_method.c
@@ -7,6 +7,7 @@
 #include <linux/kernel.h>
 #include <linux/uaccess.h>
 #include <linux/debugfs.h>
+#include <linux/module.h>
 #include <acpi/acpi_drivers.h>
 
 #include "internal.h"
@@ -29,6 +30,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 	struct acpi_table_header table;
 	acpi_status status;
 
+	if (secure_modules())
+		return -EPERM;
+
 	if (!(*ppos)) {
 		/* parse the table header to get the table length */
 		if (count <= sizeof(struct acpi_table_header))
-- 
1.8.3.1

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