From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96F55C43457 for ; Thu, 15 Oct 2020 09:44:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E65F222260 for ; Thu, 15 Oct 2020 09:44:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E65F222260 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 63A45940010; Thu, 15 Oct 2020 05:44:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5EB6E94000C; Thu, 15 Oct 2020 05:44:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 48D1F940010; Thu, 15 Oct 2020 05:44:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0123.hostedemail.com [216.40.44.123]) by kanga.kvack.org (Postfix) with ESMTP id 1CDF594000C for ; Thu, 15 Oct 2020 05:44:22 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 7E829DB58 for ; Thu, 15 Oct 2020 09:44:21 +0000 (UTC) X-FDA: 77373674322.06.bell64_1a0896d27213 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id 511E810232BD7 for ; Thu, 15 Oct 2020 09:44:21 +0000 (UTC) X-HE-Tag: bell64_1a0896d27213 X-Filterd-Recvd-Size: 2694 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf04.hostedemail.com (Postfix) with ESMTP for ; Thu, 15 Oct 2020 09:44:20 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 74692ACF6; Thu, 15 Oct 2020 09:44:19 +0000 (UTC) Subject: Re: [PATCH v3 0/3] Actually fix freelist pointer vs redzoning To: Christopher Lameter , Kees Cook Cc: Andrew Morton , Waiman Long , Marco Elver , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org References: <20201015033712.1491731-1-keescook@chromium.org> From: Vlastimil Babka Message-ID: <1e43fd23-e9f1-9c5d-3ee2-17171642877f@suse.cz> Date: Thu, 15 Oct 2020 11:44:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/15/20 10:23 AM, Christopher Lameter wrote: > On Wed, 14 Oct 2020, Kees Cook wrote: > >> Note on patch 2: Christopher NAKed it, but I actually think this is a >> reasonable thing to add -- the "too small" check is only made when built >> with CONFIG_DEBUG_VM, so it *is* actually possible for someone to trip >> over this directly, even if it would never make it into a released >> kernel. I see no reason to just leave this foot-gun in place, though, so >> we might as well just fix it too. (Which seems to be what Longman was >> similarly supporting, IIUC.) > > Well then remove the duplication of checks. The NAK was there because it > seems that you were not aware of the existing checks. > >> Anyway, if patch 2 stays NAKed, that's fine. It's entirely separable, >> and the other 2 can land. :) > > Just deal with the old checks too and it will be fine. Yeah, the existing check is under CONFIG_DEBUG_VM, which means it's not active on some configurations. Creating a cache is not exactly fast path operation, so I would remove this guard. As for the minimum size check, I would probably remove it (but watch out if SLAB/SLOB can handle it). It's not effective to use slab cache for 4-byte objects, but why make it an error.