lkml.org 
[lkml]   [2017]   [Oct]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 12/27] x86/msr: Restrict MSR access when the kernel is locked down
Hi David, 

On Mon, Oct 23, 2017 at 03:49:44PM +0100, David Howells wrote:
> Alan Cox <gnomes@lxorguk.ukuu.org.uk> wrote:
>
> > There are a load of standard tools that use this so I think you are going
> > to need a whitelist. Can you at least log *which* MSR in the failing case
> > so a whitelist can be built over time ?
>
> Will the attached change work for you?
>

It's good to me.

Joey Lee

> ---
> diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
> index a05a97863286..f18cadbc31ce 100644
> --- a/arch/x86/kernel/msr.c
> +++ b/arch/x86/kernel/msr.c
> @@ -84,8 +84,10 @@ 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"))
> + if (kernel_is_locked_down("Direct MSR access")) {
> + pr_info("Direct access to MSR %x\n", reg);
> return -EPERM;
> + }
>
> if (count % 8)
> return -EINVAL; /* Invalid chunk size */
> @@ -135,6 +137,7 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
> break;
> }
> if (kernel_is_locked_down("Direct MSR access")) {
> + pr_info("Direct access to MSR %x\n", reg[1]); /* Display %ecx */
> err = -EPERM;
> break;
> }

\
 
 \ /
  Last update: 2017-10-25 16:04    [W:0.246 / U:3.604 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site