linux-kernel - Re: [PATCH] x86/process: Silence KASAN warnings in get

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Message-ID: <CALCETrW7L=GKj4D9vLmB3u9ik5XX2zNTJO4yq8bgpxgd0XYqHQ@mail.gmail.com>
Date:	Mon, 5 Oct 2015 11:42:45 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Wolfram Gloger <wmglo@...t.med.uni-muenchen.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86/process: Silence KASAN warnings in get_wchan()

On Mon, Oct 5, 2015 at 6:15 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Mon, Oct 05, 2015 at 02:46:30PM +0300, Andrey Ryabinin wrote:
>> It's absolutely unusable:( https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
>> If we add it here, it won't built because of: '__always_inline __read_once_size()'
>>
>> But, I think I have the solution.
>> We could have some blacklist - list of function names which we should be ignored.
>> In kasan_report() we could resolve return address to function name and compare it with name in list.
>> If name in list -> ignore report.
>
> Sounds better. :)

These ought to be rare.  probe_kernel_xyz are hopefully already
covered, which leaves strange accesses to things that are known to be
out of bounds, which ought to be just the memory allocation stuff
(already covered?) and stack walking code (this stuff).

I think that READ_ONCE_NOCHECK is a decent solution that isn't too messy.

--Andy
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