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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 5 Oct 2015 19:59:38 +0300
From:	Andrey Ryabinin <aryabinin@...tuozzo.com>
To:	Andi Kleen <ak@...ux.intel.com>
CC:	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>,
	Andy Lutomirski <luto@...capital.net>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	Borislav Petkov <bp@...en8.de>,
	Denys Vlasenko <dvlasenk@...hat.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 10/05/2015 07:39 PM, Andi Kleen wrote:
>> 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.
> 
> I think annotating statements is cleaner than functions, even if it
> is more code. Much better documentation
> 

I agree with that, that's why I suggested to add READ_ONCE_NOCHECK():
	READ_ONCE_NOCHECK()
	{
		kasan_disable_current();
		READ_ONCE();
		kasan_enable_current();
	}

Anywone objects?

> But if you really want to annotate on the function level:
> 
> It's better to annotate the function directly than some hidden away list.
> This way there is some indication that there are races in there, which is
> generally useful documentation.
> 
> __racy_function or similar.
> 
> Also central lists are generally annoying as they cause patch conflicts.
> 
> If disabling with an attribute doesn't work, you could put it into a special section
> with __attribute__((section ...)) and check the start/end symbol before reporting. 
> That's how kprobes solves similar issues. It also has the advantage
> that it stops inlining.


Yes, it might be better. Although, because of broken -fconserve-stack, this may
not work in some cases - https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
Function splitter may split original function into two parts and it always puts one split
part in default .text section.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/