Received: by 2002:ad5:474a:0:0:0:0:0 with SMTP id i10csp6035338imu; Tue, 13 Nov 2018 16:11:19 -0800 (PST) X-Google-Smtp-Source: AJdET5cxhvbWHvcpa3NhFAF6+xRXBki5XHjT3n0llnFHrTrwy4mdlm9jE0M8a/6raW7cwFD8XnsF X-Received: by 2002:a17:902:15a8:: with SMTP id m37-v6mr7221289pla.256.1542154279188; Tue, 13 Nov 2018 16:11:19 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1542154279; cv=none; d=google.com; s=arc-20160816; b=COeBdvdNyUWV9rPguv6RTIWzgOfp6efTABGT4BhD0pgHmnJRYB5EE5TIVlHvdSCwdu y1is1kOcR8kfMcXXHKA3XA6l6E7wTsl/+d4u3MSv1GonIzTnfSIk6P1vkdwW0LSKAuVf BpzdoPx2OkDOWOKeUVZY4N0FNACMxp5AhV3v8bx9oHLlDK6wFkwq6FFOTCJKnar9T5vb pH8hncLEJgZZWsGKw+HvAsaqIx+bQWFIMTeqxjQzclDmb3ADQAuv3ZRJ2TbUT555tB6y aRK3Jzox1Tw0VvbRFRBZwviBzwvk0iVVSfIyZfCrFoytoN6IJPNkBPMRGL2qduthhPlT fTKw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding :content-language:in-reply-to:mime-version:user-agent:date :message-id:autocrypt:openpgp:from:references:cc:to:subject; bh=BxImjV3PfUol3PGXSKMyMWcA/NI7Ye6glEF5G9EEZkk=; b=vjMzsQ6FuJu2cdlPmIXrcQ1lSXxv750ptwpkdqPwwqQgMl1rsMoTNXR8BJKe9LleKX BPxhxNzvL8HywMwKXTDPop0NpmH1OJL9b+T13nwS+93kch2cvO+iXfaYVGwsVP/r8UAG DqslHXX3bV2noP6Zdiaj0Lha35kcuWBwY5M1tSp9PtoG6/n5FBxeJh721K/bMJhy3gPv DRTPAuU/SHEuq7ow9fh23ByPP298+E1Qz/+b/t0NTKYcCl0t/m8KH1NgPFIzVRHMsA2Y PuSGnz6oYPhtU7pwL1fhJgM/ILLl6EphZ553LNvtDCPkoX+KjnnaUHVayfKie7k65iq7 UwkQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id w3-v6si12241308plb.154.2018.11.13.16.11.04; Tue, 13 Nov 2018 16:11:19 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731825AbeKNKJR (ORCPT + 99 others); Wed, 14 Nov 2018 05:09:17 -0500 Received: from mx2.suse.de ([195.135.220.15]:53536 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726823AbeKNKJR (ORCPT ); Wed, 14 Nov 2018 05:09:17 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 1CC07AFEC; Wed, 14 Nov 2018 00:08:33 +0000 (UTC) Subject: Re: UBSAN: Undefined behaviour in mm/page_alloc.c To: Andrew Morton Cc: Michal Hocko , Kyungtae Kim , pavel.tatashin@microsoft.com, osalvador@suse.de, rppt@linux.vnet.ibm.com, aaron.lu@intel.com, iamjoonsoo.kim@lge.com, alexander.h.duyck@linux.intel.com, mgorman@techsingularity.net, lifeasageek@gmail.com, threeearcat@gmail.com, syzkaller@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Konstantin Khlebnikov References: <20181109084353.GA5321@dhcp22.suse.cz> <20181113094305.GM15120@dhcp22.suse.cz> <20181113151503.fd370e28cb9df5a0933e9b04@linux-foundation.org> <20181113153204.ea0c0895866838de9e3bc8d0@linux-foundation.org> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; prefer-encrypt=mutual; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSFWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmNvbT7CwZcEEwEKAEECGwMFCwkIBwMFFQoJCAsFFgIDAQAC HgECF4ACGQEWIQSpQNQ0mSwujpkQPVAiT6fnzIKmZAUCWi/zTwUJBbOLuQAKCRAiT6fnzIKm ZIpED/4jRN/6LKZZIT4R2xoou0nJkBGVA3nfb+mUMgi3uwn/zC+o6jjc3ShmP0LQ0cdeuSt/ t2ytstnuARTFVqZT4/IYzZgBsLM8ODFY5vGfPw00tsZMIfFuVPQX3xs0XgLEHw7/1ZCVyJVr mTzYmV3JruwhMdUvIzwoZ/LXjPiEx1MRdUQYHAWwUfsl8lUZeu2QShL3KubR1eH6lUWN2M7t VcokLsnGg4LTajZzZfq2NqCKEQMY3JkAmOu/ooPTrfHCJYMF/5dpi8YF1CkQF/PVbnYbPUuh dRM0m3NzPtn5DdyfFltJ7fobGR039+zoCo6dFF9fPltwcyLlt1gaItfX5yNbOjX3aJSHY2Vc A5T+XAVC2sCwj0lHvgGDz/dTsMM9Ob/6rRJANlJPRWGYk3WVWnbgW8UejCWtn1FkiY/L/4qJ UsqkId8NkkVdVAenCcHQmOGjRQYTpe6Cf4aQ4HGNDeWEm3H8Uq9vmHhXXcPLkxBLRbGDSHyq vUBVaK+dAwAsXn/5PlGxw1cWtur1ep7RDgG3vVQDhIOpAXAg6HULjcbWpBEFaoH720oyGmO5 kV+yHciYO3nPzz/CZJzP5Ki7Q1zqBb/U6gib2at5Ycvews+vTueYO+rOb9sfD8BFTK386LUK uce7E38owtgo/V2GV4LMWqVOy1xtCB6OAUfnGDU2EM7ATQRbGTU1AQgAn0H6UrFiWcovkh6E XVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQLa1PQDUi6j00ChlcR66g9/V0sPIcSutacPKf dKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMhFmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCT sTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sfbAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZO rIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq+aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahK tQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4njQARAQABwsF8BBgBCgAmFiEEqUDUNJksLo6Z ED1QIk+n58yCpmQFAlsZNTUCGwwFCQPCZwAACgkQIk+n58yCpmQ83g/9Frg1sRMdGPn98zV+ O2eC3h0p5f/oxxQ8MhG5znwHoW4JDG2TuxfcQuz7X7Dd5JWscjlw4VFJ2DD+IrDAGLHwPhCr RyfKalnrbYokvbClM9EuU1oUuh7k+Sg5ECNXEsamW9AiWGCaKWNDdHre3Lf4xl+RJWxghOVW RiUdpLA/a3yDvJNVr6rxkDHQ1P24ZZz/VKDyP+6g8aty2aWEU0YFNjI+rqYZb2OppDx6fdma YnLDcIfDFnkVlDmpznnGCyEqLLyMS3GH52AH13zMT9L9QYgT303+r6QQpKBIxAwn8Jg8dAlV OLhgeHXKr+pOQdFf6iu2sXlUR4MkO/5KWM1K0jFR2ug8Pb3aKOhowVMBT64G0TXhQ/kX4tZ2 ZF0QZLUCHU3Cigvbu4AWWVMNDEOGD/4sn9OoHxm6J04jLUHFUpFKDcjab4NRNWoHLsuLGjve Gdbr2RKO2oJ5qZj81K7os0/5vTAA4qHDP2EETAQcunTn6aPlkUnJ8aw6I1Rwyg7/XsU7gQHF IM/cUMuWWm7OUUPtJeR8loxZiZciU7SMvN1/B9ycPMFs/A6EEzyG+2zKryWry8k7G/pcPrFx O2PkDPy3YmN1RfpIX2HEmnCEFTTCsKgYORangFu/qOcXvM83N+2viXxG4mjLAMiIml1o2lKV cqmP8roqufIAj+Ohhzs= Message-ID: <1f4439c8-d669-a1ac-53f5-36c04da72a51@suse.cz> Date: Wed, 14 Nov 2018 01:05:33 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181113153204.ea0c0895866838de9e3bc8d0@linux-foundation.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/14/18 12:32 AM, Andrew Morton wrote: > On Wed, 14 Nov 2018 00:23:28 +0100 Vlastimil Babka wrote: > >> On 11/14/18 12:15 AM, Andrew Morton wrote: >>> On Tue, 13 Nov 2018 10:43:05 +0100 Michal Hocko wrote: >>> >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -4364,6 +4353,15 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid, >>>> gfp_t alloc_mask; /* The gfp_t that was actually used for allocation */ >>>> struct alloc_context ac = { }; >>>> >>>> + /* >>>> + * There are several places where we assume that the order value is sane >>>> + * so bail out early if the request is out of bound. >>>> + */ >>>> + if (unlikely(order >= MAX_ORDER)) { >>>> + WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN)); >>>> + return NULL; >>>> + } >>>> + >>> >>> I know "everybody enables CONFIG_DEBUG_VM", but given this is fastpath, >>> we could help those who choose not to enable it by using >>> >>> #ifdef CONFIG_DEBUG_VM >>> if (WARN_ON_ONCE(order >= MAX_ORDER && !(gfp_mask & __GFP_NOWARN))) >>> return NULL; >>> #endif >> >> Hmm, but that would mean there's still potential undefined behavior for >> !CONFIG_DEBUG_VM, so I would prefer not to do it like that. >> > > What does "potential undefined behavior" mean here? I mean that it becomes undefined once a caller with order >= MAX_ORDER appears. Worse if it's directly due to a userspace action, like in this case.