[PATCH 09/20] x86: Restrict MSR access when module loading is restricted

[Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx>]

From: Matthew Garrett <matthew.garrett@xxxxxxxxxx>

Writing to MSRs should not be allowed if module loading is restricted,
since it could lead to execution of arbitrary code in kernel mode. Based
on a patch by Kees Cook.

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

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 7f3550acde1b..963ba4011923 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -83,6 +83,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
 	int err = 0;
 	ssize_t bytes = 0;
 
+	if (secure_modules())
+		return -EPERM;
+
 	if (count % 8)
 		return -EINVAL;	/* Invalid chunk size */
 
@@ -130,6 +133,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 			err = -EBADF;
 			break;
 		}
+		if (secure_modules()) {
+			err = -EPERM;
+			break;
+		}
 		if (copy_from_user(&regs, uregs, sizeof regs)) {
 			err = -EFAULT;
 			break;
-- 
2.9.3
_______________________________________________
kernel mailing list -- kernel@xxxxxxxxxxxxxxxxxxxxxxx
To unsubscribe send an email to kernel-leave@xxxxxxxxxxxxxxxxxxxxxxx