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From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Wed, 8 Nov 2017 15:11:34 +0000
Subject: [15/29] ACPI: Limit access to custom_method when the kernel is locked
down
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=5ff99c830aacf02f25816a0da427216fb63ba16d
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.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: linux-acpi@vger.kernel.org
---
drivers/acpi/custom_method.c | 3 +++
1 file changed, 3 insertions(+)
Index: linux/drivers/acpi/custom_method.c
===================================================================
--- linux.orig/drivers/acpi/custom_method.c
+++ linux/drivers/acpi/custom_method.c
@@ -29,6 +29,9 @@ static ssize_t cm_write(struct file *fil
struct acpi_table_header table;
acpi_status status;
+ if (kernel_is_locked_down("ACPI custom methods"))
+ return -EPERM;
+
if (!(*ppos)) {
/* parse the table header to get the table length */
if (count <= sizeof(struct acpi_table_header))
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