Re: [PATCH 1/3] x86/init: Fix cr4_init_shadow() on CR4-less machines

[Borislav Petkov]

On Wed, Sep 28, 2016 at 12:34:14PM -0700, Andy Lutomirski wrote:
> cr4_init_shadow() will panic on 486-like machines without CR4.  Fix
> it using __read_cr4_safe().
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: david@xxxxxxxxxxxxxx
> Fixes: 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4")
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> ---
>  arch/x86/include/asm/tlbflush.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> index 6fa85944af83..dee8a70382ba 100644
> --- a/arch/x86/include/asm/tlbflush.h
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -81,7 +81,7 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate);
>  /* Initialize cr4 shadow for this CPU. */
>  static inline void cr4_init_shadow(void)
>  {
> -	this_cpu_write(cpu_tlbstate.cr4, __read_cr4());
> +	this_cpu_write(cpu_tlbstate.cr4, __read_cr4_safe());
>  }
>  
>  /* Set in this cpu's CR4. */
> -- 

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

-- 
Regards/Gruss,
    Boris.

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