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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 A418BC3F2D1 for ; Wed, 4 Mar 2020 13:17:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 654A220838 for ; Wed, 4 Mar 2020 13:17:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 654A220838 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 CFBA36B0003; Wed, 4 Mar 2020 08:17:09 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CD3976B0005; Wed, 4 Mar 2020 08:17:09 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C0F806B0006; Wed, 4 Mar 2020 08:17:09 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0093.hostedemail.com [216.40.44.93]) by kanga.kvack.org (Postfix) with ESMTP id A5AE16B0003 for ; Wed, 4 Mar 2020 08:17:09 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 4701D8248047 for ; Wed, 4 Mar 2020 13:17:09 +0000 (UTC) X-FDA: 76557730578.09.store80_789d3c9e8931e X-HE-Tag: store80_789d3c9e8931e X-Filterd-Recvd-Size: 2242 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf25.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Mar 2020 13:17:08 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id D2757AFF0; Wed, 4 Mar 2020 13:17:06 +0000 (UTC) Subject: Re: SLUB: sysfs lets root force slab order below required minimum, causing memory corruption To: Jann Horn , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton Cc: Linux-MM , kernel list , Kees Cook , Matthew Garrett References: From: Vlastimil Babka Message-ID: Date: Wed, 4 Mar 2020 14:17:04 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 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 3/4/20 1:23 AM, Jann Horn wrote: > Hi! > > FYI, I noticed that if you do something like the following as root, > the system blows up pretty quickly with error messages about stuff > like corrupt freelist pointers because SLUB actually allows root to > force a page order that is smaller than what is required to store a > single object: > > echo 0 > /sys/kernel/slab/task_struct/order > > The other SLUB debugging options, like red_zone, also look kind of > suspicious with regards to races (either racing with other writes to > the SLUB debugging options, or with object allocations). Yeah I also wondered last week that there seems to be no sychronization with alloc/free activity. Increasing order is AFAICS also dangerous with freelist randomization: https://lore.kernel.org/linux-mm/d3acc069-a5c6-f40a-f95c-b546664bc4ee@suse.cz/