linux-kernel - Re: [PATCH 1/3] x86/init: Fix cr4_init

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Message-ID: <20160929114447.GB10578@nazgul.tnic>
Date:   Thu, 29 Sep 2016 13:44:47 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     x86@...nel.org, david@...giorato.net,
        Brian Gerst <brgerst@...il.com>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/3] x86/init: Fix cr4_init_shadow() on CR4-less machines

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@...r.kernel.org
> Reported-by: david@...giorato.net
> Fixes: 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4")
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---
>  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@...e.de>

-- 
Regards/Gruss,
    Boris.

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