[PATCH 06/12] acpi: Limit access to custom_method if securelevel is set

[Matthew Garrett]

custom_method effectively allows arbitrary access to system memory, making
it possible for an attacker to modify the kernel at runtime. Prevent this
if securelevel has been set.

Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
---
 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..8b881db 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/security.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 (get_securelevel() > 0)
+		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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