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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 77AAFC2BA2B for ; Thu, 16 Apr 2020 06:14:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 188EF2078A for ; Thu, 16 Apr 2020 06:14:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=web.de header.i=@web.de header.b="fnz5YT8N" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 188EF2078A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=web.de Authentication-Results: mail.kernel.org; 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Thu, 16 Apr 2020 06:14:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=web.de; s=dbaedf251592; t=1587017649; bh=yE3WRQFbzy9TZxF3eQPkIGcnX6B9c+jYyC2kI29aWMk=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=fnz5YT8NWV94IsnzLzg8HgmsXko0cm3fapuGIKC2PC7NQZxkqk1P2/fvHpT93GUQu IA7VaM5mS1fau5ng+Lorwb4Z4ChVpsGpch4JyA99nCk+KataGoo/u+hiMl2Snu4NFv RvD3wp8K4pZ3kxL5vDhedDO+W0IH4Smds1MUpUGI= X-UI-Sender-Class: c548c8c5-30a9-4db5-a2e7-cb6cb037b8f9 Received: from [192.168.1.3] ([2.243.109.113]) by smtp.web.de (mrweb103 [213.165.67.124]) with ESMTPSA (Nemesis) id 0MVLak-1jlOTn0EYA-00YfQo; Thu, 16 Apr 2020 08:14:09 +0200 Subject: Re: [PATCH v4] mm/ksm: Fix NULL pointer dereference when KSM zero page is enabled To: Andrew Morton , Muchun Song , Xiongchun Duan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Kirill Tkhai , Yang Shi References: <20200416025034.29780-1-songmuchun@bytedance.com> <20200415195841.da4361916f662a0136a271a5@linux-foundation.org> From: Markus Elfring Autocrypt: addr=Markus.Elfring@web.de; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200415195841.da4361916f662a0136a271a5@linux-foundation.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:hruyfe80HoKoDtVWzyXWpdMt82R75FeTYIsTEIQFpTkH1L8Nu+o lAwuc9XEJ2+0Dk5Fc0Q6CYathRlKeRsy/Kv6OeZGoGMC/QJU/6L+fMQbsw4t9PlqQVgK83p TrCyZGQmWFu/pyhIFFYVQDcA6rr15iaMC+oFAhwoJoMqE9F9+gPxf0ZQGK6OVvjtd4jg0qG dIZTN20xmgPlKlbwt22mA== X-UI-Out-Filterresults: notjunk:1;V03:K0:QRbQ1/dJKzc=:1GZqrtpF/61F7ORjcJLWGY zeen+Xs8iyH9Cj/YMb0eFBL5VgfSLpqAPZdtHMNloybZ/g0RsT1FvA3JxaRl6Cn7H16bQwuen inUkmshyYK5dy79PXyUAlv6g0ApZBmNfx+Jan8Lkvp6UkmjWM7V1WOt5LH/AdJpgFt0Hs7G89 UP9eYygtAJutKXpGQfWMMo/5Hr/h3khGpMXU9c2BaXNAqbeg970q791nO7iKfn0aVTe6l4lHk zR8Ups+G5ttVryZZ0txhVh272pbUACPPtxlgNFNintEI47qpZ2js5Dz8/88r8XsvBcEbSSBWi SAjqGKOqFJtYCiXy7J20jyhy4EDS8iZlOH7IRze1bOYLsh3HJ3/nhb/6zWuoi7mUaLsUhp63b HsboVUc5djT4TBCWXFSSpSXIZHg7X7VLl7XOiXQLOvj2QPREZmK9oiNwAOmJzjlmUMNH0HUok qvM1VHNuNPsTZAb4k/oi1K5U3CHTpfu+w03ePHOwVwkFsUIhQPqeNS1f1vizjCwZFd1YPdgqm xCeTqAs5NNpkQDN/0swjjePXAPW0XcWZNnJX5RIO+6wSEKOfNpGlC8/4ubMZFw9Bn6qPsG/0P YbRdfhlCwUGBEgXowJlG2h1oifU53ldQRONuKBJ2tn2V+wwxVoV33yjkVL52MewxJexok4QKz Dcvm1Dt9bIDGh1FhXDTIGff5Q189t5rsJpeMMf3gPWk6eAlwiAZrWwELqzqBTQcuhk0H5Y5QU 8qYk16r3JuoJOwiEZULjMmhYkW6xVbR2l7GPuZqzNA8auEFuw0AFp5yQ+5aj0d9rb7PyroaWP 20SnDDlSmGaSLNsCUV+iD1YYq9zmOYI2JpOZeI66QnejfanC7VBCmcZa63SeX0u9h+3um8PMT Fo5m7poJsWYctm16DA1XpTNPmxjQpejlyYwIhQ1Z9O1vbFQiGL55xXz5746M3HwI6Q3u+VFBD Il77XE6d44Y2x5Ko3OJAR0578tsCSxvEbJiomr4rjsG0Z8S/ipDbvliRCQIr47JhySIqVCXZ5 7EyjBIS6e3WgcUFXblUHtVfxhcu9UbMSej8LhoiTUgmlI5IW6u00j12JzaZwJgOJ57V+nSXRu rLQVV2T1sQuq86e7xDw61STR6HprDd93e/nTKoeSND/Md8NduKcLNaZ3updBV5UEI7R2zSsj7 SRuJ3Y3iwFrjC1CcI9sVRtjcGmRfPt4wcnRds1g9lCis2llWlNel+zf9G235vCaMbfTPfZPgf KnjiESZZ5QhNV7L7Q X-Bogosity: Ham, tests=bogofilter, spamicity=0.000401, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: =E2=80=A6 >> +++ b/mm/ksm.c >> @@ -2112,8 +2112,15 @@ static void cmp_and_merge_page(struct page *page= , struct rmap_item *rmap_item) =E2=80=A6 >> + if (vma) >> + err =3D try_to_merge_one_page(vma, page, >> + ZERO_PAGE(rmap_item->address)); >> + else >> + /** >> + * If the vma is out of date, we do not need to >> + * continue. >> + */ >> + err =3D 0; >> up_read(&mm->mmap_sem); =E2=80=A6 > It's conventional to put braces around multi-line blocks such as this. Are there different views to consider around the usage of single statement= s together with curly brackets in if branches? Regards, Markus