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Date: Wed, 22 Nov 2017 07:19:23 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc: X86 ML <x86@kernel.org>, Borislav Petkov <bpetkov@suse.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Brian Gerst <brgerst@gmail.com>, Dave Hansen <dave.hansen@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>, kasan-dev@googlegroups.com
Subject: Re: [PATCH v2 06/18] x86/kasan/64: Teach KASAN about the
 cpu_entry_area
Message-ID: <20171122061923.o7wctfxkivgk63g4@gmail.com>
References: <cover.1511325444.git.luto@kernel.org>
 <02da46906066215f87e15a7a406109e353f4381a.1511325444.git.luto@kernel.org>
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* Andy Lutomirski <luto@kernel.org> wrote:

> The cpu_entry_area will contain stacks.  Make sure that KASAN has
> appropriate shadow mappings for them.
> 
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: kasan-dev@googlegroups.com
> Signed-off-by: Andy Lutomirski <luto@kernel.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)),
> +		0);
> +
> +	kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_TOP) + PAGE_SIZE)),
> +				   (void *)KASAN_SHADOW_END);

Note, this commit has a dependency on:

  d17a1d97dc20: x86/mm/kasan: don't use vmemmap_populate() to initialize shadow

which got merged upstream outside the x86 tree, so it has a whole bunch of merge 
window dependencies.

To make testing+backporting to v4.14 easier I've cherry-picked d17a1d97dc20 into 
x86/urgent.

( I've Cc:-ed Linus, just in case this kind of preemptive cherry-picking is 
  frowned upon. )

Thanks,

	Ingo