linux-kernel - Re: [PATCH v2 5/5] arm64: add KASan support

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, 24 Aug 2015 18:47:36 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Keitel <dkeitel@...eaurora.org>,
	Alexander Potapenko <glider@...gle.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v2 5/5] arm64: add KASan support

On Mon, Aug 24, 2015 at 05:15:22PM +0300, Andrey Ryabinin wrote:
> Yes, ~130Mb (3G/1G split) should work. 512Mb shadow is optional.
> The only advantage of 512Mb shadow is better handling of user memory
> accesses bugs
> (access to user memory without copy_from_user/copy_to_user/strlen_user etc API).

No need for that to be handed by KASan.  I have patches in linux-next,
now acked by Will, which prevent the kernel accessing userspace with
zero memory footprint.  No need for remapping, we have a way to quickly
turn off access to userspace mapped pages on non-LPAE 32-bit CPUs.
(LPAE is not supported yet - Catalin will be working on that using the
hooks I'm providing once he returns.)

This isn't a debugging thing, it's a security hardening thing.  Some
use-after-free bugs are potentially exploitable from userspace.  See
the recent blackhat conference paper.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
--
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/