From aa2c63fe074c0074a44cc89641e955ba9948e428 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg59@srcf.ucam.org>
Date: Fri, 8 Feb 2013 11:12:13 -0800
Subject: [PATCH 10/16] x86: Restrict MSR access when securelevel is set
Patch-mainline: Queued in subsystem maintainer repository
Git-repo: https://github.com/mjg59/linux
Git-commit: aa2c63fe074c0074a44cc89641e955ba9948e428
References: fate#320387
Permitting write access to MSRs allows userspace to modify the running
kernel. Prevent this if securelevel has been set. Based on a patch by Kees
Cook.
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
arch/x86/kernel/msr.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -39,6 +39,7 @@
#include <linux/notifier.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
+#include <linux/security.h>
#include <asm/processor.h>
#include <asm/msr.h>
@@ -105,6 +106,9 @@ static ssize_t msr_write(struct file *fi
int err = 0;
ssize_t bytes = 0;
+ if (get_securelevel() > 0)
+ return -EPERM;
+
if (count % 8)
return -EINVAL; /* Invalid chunk size */
@@ -152,6 +156,10 @@ static long msr_ioctl(struct file *file,
err = -EBADF;
break;
}
+ if (get_securelevel() > 0) {
+ err = -EPERM;
+ break;
+ }
if (copy_from_user(®s, uregs, sizeof regs)) {
err = -EFAULT;
break;