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.garr...@nebula.com>
---
 drivers/acpi/custom_method.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
index 12b62f2..50647b3 100644
--- a/drivers/acpi/custom_method.c
+++ b/drivers/acpi/custom_method.c
@@ -29,6 +29,9 @@ 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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