Patchwork [11/12] x86: Require CAP_COMPROMISE_KERNEL for MSR writing

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Submitter Matthew Garrett
Date March 18, 2013, 9:32 p.m.
Message ID <1363642353-30749-11-git-send-email-matthew.garrett@nebula.com>
Download mbox | patch
Permalink /patch/228822/
State Not Applicable
Headers show

Comments

Matthew Garrett - March 18, 2013, 9:32 p.m.
From: Kees Cook <keescook@chromium.org>

Writing to MSRs should not be allowed unless CAP_COMPROMISE_KERNEL is
set since it could lead to execution of arbitrary code in kernel mode.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 arch/x86/kernel/msr.c | 7 +++++++
 1 file changed, 7 insertions(+)

Patch

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index ce13049..fa4dc6c 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -103,6 +103,9 @@  static ssize_t msr_write(struct file *file, const char __user *buf,
 	int err = 0;
 	ssize_t bytes = 0;
 
+	if (!capable(CAP_COMPROMISE_KERNEL))
+		return -EPERM;
+
 	if (count % 8)
 		return -EINVAL;	/* Invalid chunk size */
 
@@ -150,6 +153,10 @@  static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 			err = -EBADF;
 			break;
 		}
+		if (!capable(CAP_COMPROMISE_KERNEL)) {
+			err = -EPERM;
+			break;
+		}
 		if (copy_from_user(&regs, uregs, sizeof regs)) {
 			err = -EFAULT;
 			break;