linux-kernel - Re: [PATCH v2 06/18] x86/kasan/64: Teach KASAN about the cpu_entry

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Date:   Wed, 22 Nov 2017 12:05:21 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>
Cc:     Borislav Petkov <bpetkov@...e.de>,
        "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>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com
Subject: Re: [PATCH v2 06/18] x86/kasan/64: Teach KASAN about the
 cpu_entry_area



On 11/22/2017 07:44 AM, Andy Lutomirski wrote:
> The cpu_entry_area will contain stacks.  Make sure that KASAN has
> appropriate shadow mappings for them.
> 
> Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Cc: Alexander Potapenko <glider@...gle.com>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: kasan-dev@...glegroups.com
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---
>  arch/x86/mm/kasan_init_64.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
> index 99dfed6dfef8..43d376687315 100644
> --- a/arch/x86/mm/kasan_init_64.c
> +++ b/arch/x86/mm/kasan_init_64.c
> @@ -330,7 +330,14 @@ void __init kasan_init(void)
>  			      early_pfn_to_nid(__pa(_stext)));
>  
>  	kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
> -			(void *)KASAN_SHADOW_END);
> +				   kasan_mem_to_shadow((void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_BOTTOM))));
> +
> +	kasan_populate_shadow((unsigned long)kasan_mem_to_shadow((void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_BOTTOM))),
> +			      (unsigned long)kasan_mem_to_shadow((void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_TOP) + PAGE_SIZE)),

What's '+ PAGE_SIZE' for?

> +		0);
> +
> +	kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_TOP) + PAGE_SIZE)),
> +				   (void *)KASAN_SHADOW_END);
>  
>  	load_cr3(init_top_pgt);
>  	__flush_tlb_all();
>