[PATCH 06/12] acpi: Limit access to custom_method if trusted_kernel is true

From: Matthew Garrett
Date: Fri Mar 13 2015 - 17:39:52 EST


custom_method effectively allows arbitrary access to system memory, making
it possible for an attacker to modify the kernel at runtime. Prevent this
if trusted_kernel is true.

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 c68e724..774bb7b 100644
--- a/drivers/acpi/custom_method.c
+++ b/drivers/acpi/custom_method.c
@@ -8,6 +8,7 @@
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/acpi.h>
+#include <linux/security.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_trusted_kernel())
+ return -EPERM;
+
if (!(*ppos)) {
/* parse the table header to get the table length */
if (count <= sizeof(struct acpi_table_header))
--
2.1.0

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