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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 */

1
include/linux/security.h
View File

@ -110,6 +110,7 @@ enum lockdown_reason {
LOCKDOWN_PCI_ACCESS,
LOCKDOWN_IOPORT,
LOCKDOWN_MSR,
LOCKDOWN_ACPI_TABLES,
LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_CONFIDENTIALITY_MAX,
};

1
security/lockdown/lockdown.c
View File

@ -25,6 +25,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
[LOCKDOWN_PCI_ACCESS] = "direct PCI access",
[LOCKDOWN_IOPORT] = "raw io port access",
[LOCKDOWN_MSR] = "raw MSR access",
[LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables",
[LOCKDOWN_INTEGRITY_MAX] = "integrity",
[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
};