From 3e871cf75f3ebcafd9fbdb9146adeced320c9bb3 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Wed, 5 Apr 2017 17:40:30 +0100 Subject: [PATCH] x86: Restrict MSR access when the kernel is locked down Writing to MSRs should not be allowed if the kernel is locked down, since it could lead to execution of arbitrary code in kernel mode. Based on a patch by Kees Cook. Cc: Kees Cook Signed-off-by: Matthew Garrett Signed-off-by: David Howells Gbp-Pq: Topic features/all/lockdown Gbp-Pq: Name 0051-x86-Restrict-MSR-access-when-the-kernel-is-locked-do.patch --- 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 ef688804f80..fbcce028e50 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -84,6 +84,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf, int err = 0; ssize_t bytes = 0; + if (kernel_is_locked_down()) + return -EPERM; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -131,6 +134,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) err = -EBADF; break; } + if (kernel_is_locked_down()) { + err = -EPERM; + break; + } if (copy_from_user(®s, uregs, sizeof regs)) { err = -EFAULT; break; -- 2.30.2