Re: [PATCH 14/24] x86: Restrict MSR access when the kernel is locked down

2017-04-14 Thread Thomas Gleixner 
On Wed, 5 Apr 2017, David Howells wrote:

Can you please change the subsys in $subject to 'x86/msr:' ?

> From: Matthew Garrett 
> 
> 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 
> Signed-off-by: David Howells 
> Acked-by: Kees Cook 
> cc: x...@kernel.org

Reviewed-by: Thomas Gleixner

Re: [PATCH 14/24] x86: Restrict MSR access when the kernel is locked down

2017-04-14 Thread Thomas Gleixner 
On Wed, 5 Apr 2017, David Howells wrote:

Can you please change the subsys in $subject to 'x86/msr:' ?

> From: Matthew Garrett 
> 
> 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 
> Signed-off-by: David Howells 
> Acked-by: Kees Cook 
> cc: x...@kernel.org

Reviewed-by: Thomas Gleixner

Re: [PATCH 14/24] x86: Restrict MSR access when the kernel is locked down

2017-04-05 Thread Kees Cook 
On Wed, Apr 5, 2017 at 10:12 AM, David Howells  wrote:
> From: Matthew Garrett 
>
> 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 

Acked-by: Kees Cook 

-Kees

> ---
>
>  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..fbcce028e502 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(, uregs, sizeof regs)) {
> err = -EFAULT;
> break;
>



-- 
Kees Cook
Pixel Security

Re: [PATCH 14/24] x86: Restrict MSR access when the kernel is locked down

2017-04-05 Thread Kees Cook 
On Wed, Apr 5, 2017 at 10:12 AM, David Howells  wrote:
> From: Matthew Garrett 
>
> 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 

Acked-by: Kees Cook 

-Kees

> ---
>
>  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..fbcce028e502 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(, uregs, sizeof regs)) {
> err = -EFAULT;
> break;
>



-- 
Kees Cook
Pixel Security