Hi David,
On Mon, Oct 23, 2017 at 03:49:44PM +0100, David Howells wrote:
> Alan Cox <gnomes@xxxxxxxxxxxxxxxxxxx> 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;
> }
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