From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f182.google.com (mail-wi0-f182.google.com [209.85.212.182]) by kanga.kvack.org (Postfix) with ESMTP id 345076B0038 for ; Mon, 24 Aug 2015 13:47:53 -0400 (EDT) Received: by wicja10 with SMTP id ja10so79043494wic.1 for ; Mon, 24 Aug 2015 10:47:52 -0700 (PDT) Received: from pandora.arm.linux.org.uk (pandora.arm.linux.org.uk. [2001:4d48:ad52:3201:214:fdff:fe10:1be6]) by mx.google.com with ESMTPS id u20si33478089wjw.176.2015.08.24.10.47.50 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 24 Aug 2015 10:47:51 -0700 (PDT) Date: Mon, 24 Aug 2015 18:47:36 +0100 From: Russell King - ARM Linux Subject: Re: [PATCH v2 5/5] arm64: add KASan support Message-ID: <20150824174736.GD7557@n2100.arm.linux.org.uk> References: <55AE56DB.4040607@samsung.com> <20150824131557.GB7557@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Ryabinin Cc: Linus Walleij , Arnd Bergmann , "linux-mm@kvack.org" , Catalin Marinas , Will Deacon , "linux-kernel@vger.kernel.org" , David Keitel , Alexander Potapenko , "linux-arm-kernel@lists.infradead.org" , Andrew Morton , Dmitry Vyukov 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org