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ACPI: Limit access to custom_method when the kernel is locked down

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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 <mjg59@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: linux-acpi@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Matthew Garrett
2019-08-19 17:17:50 -07:00
committed by James Morris
parent 95f5e95f41
commit f474e1486b
3 changed files with 8 additions and 0 deletions
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6
drivers/acpi/custom_method.c
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@@ -9,6 +9,7 @@
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/acpi.h>
#include <linux/security.h>
#include "internal.h"
@@ -29,6 +30,11 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
struct acpi_table_header table;
acpi_status status;
int ret;
ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
if (ret)
return ret;
if (!(*ppos)) {
/* parse the table header to get the table length */