linux-kernel - Re: [PATCH 16/18] x86/boot/32: Fix cpu_current_top_of

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Message-ID: <20171101101828.vtrh2y47zmobqrwj@pd.tnic>
Date:   Wed, 1 Nov 2017 11:18:29 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 16/18] x86/boot/32: Fix cpu_current_top_of_stack
 initialization at boot

On Thu, Oct 26, 2017 at 01:26:48AM -0700, Andy Lutomirski wrote:
> cpu_current_top_of_stack's initialization forgot about
> TOP_OF_KERNEL_STACK_PADDING.  This bug didn't matter because the
> idle threads never enter user mode.
> 
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---
>  arch/x86/kernel/smpboot.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index ad59edd84de7..06c18fe1c09e 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -961,8 +961,7 @@ void common_cpu_up(unsigned int cpu, struct task_struct *idle)
>  #ifdef CONFIG_X86_32
>  	/* Stack for startup_32 can be just as for start_secondary onwards */
>  	irq_ctx_init(cpu);
> -	per_cpu(cpu_current_top_of_stack, cpu) =
> -		(unsigned long)task_stack_page(idle) + THREAD_SIZE;
> +	per_cpu(cpu_current_top_of_stack, cpu) = task_top_of_stack(idle);
>  #else
>  	initial_gs = per_cpu_offset(cpu);
>  #endif
> -- 

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--