Re: [PATCH 12/27] x86/msr: Restrict MSR access when the kernel is locked down
From: joeyli <jlee@suse.com>
Date: 2017-10-20 06:44:04
Also in:
linux-security-module, lkml
On Thu, Oct 19, 2017 at 03:52:04PM +0100, David Howells wrote:
From: Matthew Garrett <redacted> 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. Signed-off-by: Matthew Garrett <redacted> Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Kees Cook <redacted> Reviewed-by: Thomas Gleixner <redacted>
I have reviewed this patch. Please feel free to add: Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com> Thanks! Joey Lee
quoted hunk ↗ jump to hunk
cc: x86@kernel.org --- 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 ef688804f80d..a05a97863286 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("Direct MSR access")) + 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("Direct MSR access")) { + err = -EPERM; + break; + } if (copy_from_user(®s, uregs, sizeof regs)) { err = -EFAULT; break; --To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html