kernel/kexec-Disable-at-runtime-if-the-kernel-enforces-modu.patch

From 6306cad6e5663424c08e5ebdfdcfd799c5537bfe Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Fri, 9 Aug 2013 03:33:56 -0400
Subject: [PATCH] kexec: Disable at runtime if the kernel enforces module
 loading restrictions

kexec permits the loading and execution of arbitrary code in ring 0, which
is something that module signing enforcement is meant to prevent. It makes
sense to disable kexec in this situation.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 kernel/kexec.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 4c5edc357923..db431971dbd4 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -10,6 +10,7 @@
 #include <linux/mm.h>
 #include <linux/file.h>
 #include <linux/kexec.h>
+#include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/list.h>
 #include <linux/syscalls.h>
@@ -133,6 +134,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 		return -EPERM;
 
 	/*
+	 * kexec can be used to circumvent module loading restrictions, so
+	 * prevent loading in that case
+	 */
+	if (secure_modules())
+		return -EPERM;
+
+	/*
 	 * Verify we have a legal set of flags
 	 * This leaves us room for future extensions.
 	 */
-- 
2.4.3