linux-kernel - Re: [PATCH 1/2] x86/kasan: clear kasan_zero

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]

Message-ID: <CALCETrUJfc10=gGPYruw8MLvAGm+5VKP2bj8ex1Y=oXaMUA6Jg@mail.gmail.com>
Date:	Mon, 18 Jan 2016 14:24:06 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:	Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>,
	X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86/kasan: clear kasan_zero_page after TLB flush

On Mon, Jan 11, 2016 at 4:51 AM, Andrey Ryabinin
<aryabinin@...tuozzo.com> wrote:
> Currently we clear kasan_zero_page before __flush_tlb_all(). This
> works with current implementation of native_flush_tlb[_global]()
> because it doesn't cause do any writes to kasan shadow memory.
> But any subtle change made in native_flush_tlb*() could break this.
> Also current code seems doesn't work for paravirt guests (lguest).
>
> Only after the TLB flush we can be sure that kasan_zero_page is not
> used as early shadow anymore (instrumented code will not write to it).
> So it should cleared it only after the TLB flush.

This seems to fix the issue with my patch set.  Thanks.

Tested-by: Andy Lutomirski <luto@...nel.org>

--Andy