From: Matthew Garrett <matthew.garrett(a)nebula.com>
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(a)chromium.org>
Signed-off-by: Matthew Garrett <matthew.garrett(a)nebula.com>
---
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(®s, uregs, sizeof regs)) {
err = -EFAULT;
break;
--
2.9.3