[PATCH 16/24] ACPI: Limit access to custom_method when the kernel is locked down

[David Howells]

From: Matthew Garrett <matthew.garr...@nebula.com>

custom_method effectively allows arbitrary access to system memory, making
it possible for an attacker to circumvent restrictions on module loading.
Disable it if the kernel is locked down.

Signed-off-by: Matthew Garrett <matthew.garr...@nebula.com>
Signed-off-by: David Howells <dhowe...@redhat.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 c68e72414a67..e4d721c330c0 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 (kernel_is_locked_down())
+               return -EPERM;
+
        if (!(*ppos)) {
                /* parse the table header to get the table length */
                if (count <= sizeof(struct acpi_table_header))