From: Matthew Garrett <mjg59@srcf.ucam.org>
Date: Wed, 8 Nov 2017 15:11:33 +0000
Subject: [10/29] uswsusp: Disable when the kernel is locked down
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=706def46d58e9c69e91db506305485731f615e44

uswsusp allows a user process to dump and then restore kernel state, which
makes it possible to modify the running kernel.  Disable this if the kernel
is locked down.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
cc: linux-pm@vger.kernel.org
---
 kernel/power/user.c | 3 +++
 1 file changed, 3 insertions(+)

Index: linux/kernel/power/user.c
===================================================================
--- linux.orig/kernel/power/user.c
+++ linux/kernel/power/user.c
@@ -52,6 +52,9 @@ static int snapshot_open(struct inode *i
 	if (!hibernation_available())
 		return -EPERM;
 
+	if (kernel_is_locked_down("/dev/snapshot"))
+		return -EPERM;
+
 	lock_system_sleep();
 
 	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {