From: David Howells <dhowells@redhat.com>
Date: Wed, 8 Nov 2017 15:11:36 +0000
Subject: [23/29] x86/mmiotrace: Lock down the testmmiotrace module
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=20af3be0bcf6a78e3632770561fba6531dd3b444

The testmmiotrace module shouldn't be permitted when the kernel is locked
down as it can be used to arbitrarily read and write MMIO space.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Howells <dhowells@redhat.com
cc: Thomas Gleixner <tglx@linutronix.de>
cc: Steven Rostedt <rostedt@goodmis.org>
cc: Ingo Molnar <mingo@kernel.org>
cc: "H. Peter Anvin" <hpa@zytor.com>
cc: x86@kernel.org
---
 arch/x86/mm/testmmiotrace.c | 3 +++
 1 file changed, 3 insertions(+)

Index: linux/arch/x86/mm/testmmiotrace.c
===================================================================
--- linux.orig/arch/x86/mm/testmmiotrace.c
+++ linux/arch/x86/mm/testmmiotrace.c
@@ -115,6 +115,9 @@ static int __init init(void)
 {
 	unsigned long size = (read_far) ? (8 << 20) : (16 << 10);
 
+	if (kernel_is_locked_down("MMIO trace testing"))
+		return -EPERM;
+
 	if (mmio_address == 0) {
 		pr_err("you have to use the module argument mmio_address.\n");
 		pr_err("DO NOT LOAD THIS MODULE UNLESS YOU REALLY KNOW WHAT YOU ARE DOING!\n");