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[23.128.96.18]) by mx.google.com with ESMTP id b9si12036358eds.201.2020.04.15.23.15.46; Wed, 15 Apr 2020 23:16:11 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@web.de header.s=dbaedf251592 header.b=fnz5YT8N; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407384AbgDPGOb (ORCPT + 99 others); Thu, 16 Apr 2020 02:14:31 -0400 Received: from mout.web.de ([212.227.17.11]:54495 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2407264AbgDPGO1 (ORCPT ); Thu, 16 Apr 2020 02:14:27 -0400 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; prefer-encrypt=mutual; keydata= mQINBFg2+xABEADBJW2hoUoFXVFWTeKbqqif8VjszdMkriilx90WB5c0ddWQX14h6w5bT/A8 +v43YoGpDNyhgA0w9CEhuwfZrE91GocMtjLO67TAc2i2nxMc/FJRDI0OemO4VJ9RwID6ltwt mpVJgXGKkNJ1ey+QOXouzlErVvE2fRh+KXXN1Q7fSmTJlAW9XJYHS3BDHb0uRpymRSX3O+E2 lA87C7R8qAigPDZi6Z7UmwIA83ZMKXQ5stA0lhPyYgQcM7fh7V4ZYhnR0I5/qkUoxKpqaYLp YHBczVP+Zx/zHOM0KQphOMbU7X3c1pmMruoe6ti9uZzqZSLsF+NKXFEPBS665tQr66HJvZvY GMDlntZFAZ6xQvCC1r3MGoxEC1tuEa24vPCC9RZ9wk2sY5Csbva0WwYv3WKRZZBv8eIhGMxs rcpeGShRFyZ/0BYO53wZAPV1pEhGLLxd8eLN/nEWjJE0ejakPC1H/mt5F+yQBJAzz9JzbToU 5jKLu0SugNI18MspJut8AiA1M44CIWrNHXvWsQ+nnBKHDHHYZu7MoXlOmB32ndsfPthR3GSv jN7YD4Ad724H8fhRijmC1+RpuSce7w2JLj5cYj4MlccmNb8YUxsE8brY2WkXQYS8Ivse39MX BE66MQN0r5DQ6oqgoJ4gHIVBUv/ZwgcmUNS5gQkNCFA0dWXznQARAQABtCZNYXJrdXMgRWxm cmluZyA8TWFya3VzLkVsZnJpbmdAd2ViLmRlPokCVAQTAQgAPhYhBHDP0hzibeXjwQ/ITuU9 Figxg9azBQJYNvsQAhsjBQkJZgGABQsJCAcCBhUICQoLAgQWAgMBAh4BAheAAAoJEOU9Figx g9azcyMP/iVihZkZ4VyH3/wlV3nRiXvSreqg+pGPI3c8J6DjP9zvz7QHN35zWM++1yNek7Ar OVXwuKBo18ASlYzZPTFJZwQQdkZSV+atwIzG3US50ZZ4p7VyUuDuQQVVqFlaf6qZOkwHSnk+ CeGxlDz1POSHY17VbJG2CzPuqMfgBtqIU1dODFLpFq4oIAwEOG6fxRa59qbsTLXxyw+PzRaR LIjVOit28raM83Efk07JKow8URb4u1n7k9RGAcnsM5/WMLRbDYjWTx0lJ2WO9zYwPgRykhn2 sOyJVXk9xVESGTwEPbTtfHM+4x0n0gC6GzfTMvwvZ9G6xoM0S4/+lgbaaa9t5tT/PrsvJiob kfqDrPbmSwr2G5mHnSM9M7B+w8odjmQFOwAjfcxoVIHxC4Cl/GAAKsX3KNKTspCHR0Yag78w i8duH/eEd4tB8twcqCi3aCgWoIrhjNS0myusmuA89kAWFFW5z26qNCOefovCx8drdMXQfMYv g5lRk821ZCNBosfRUvcMXoY6lTwHLIDrEfkJQtjxfdTlWQdwr0mM5ye7vd83AManSQwutgpI q+wE8CNY2VN9xAlE7OhcmWXlnAw3MJLW863SXdGlnkA3N+U4BoKQSIToGuXARQ14IMNvfeKX NphLPpUUnUNdfxAHu/S3tPTc/E/oePbHo794dnEm57LuuQINBFg2+xABEADZg/T+4o5qj4cw nd0G5pFy7ACxk28mSrLuva9tyzqPgRZ2bdPiwNXJUvBg1es2u81urekeUvGvnERB/TKekp25 4wU3I2lEhIXj5NVdLc6eU5czZQs4YEZbu1U5iqhhZmKhlLrhLlZv2whLOXRlLwi4jAzXIZAu 76mT813jbczl2dwxFxcT8XRzk9+dwzNTdOg75683uinMgskiiul+dzd6sumdOhRZR7YBT+xC wzfykOgBKnzfFscMwKR0iuHNB+VdEnZw80XGZi4N1ku81DHxmo2HG3icg7CwO1ih2jx8ik0r riIyMhJrTXgR1hF6kQnX7p2mXe6K0s8tQFK0ZZmYpZuGYYsV05OvU8yqrRVL/GYvy4Xgplm3 DuMuC7/A9/BfmxZVEPAS1gW6QQ8vSO4zf60zREKoSNYeiv+tURM2KOEj8tCMZN3k3sNASfoG fMvTvOjT0yzMbJsI1jwLwy5uA2JVdSLoWzBD8awZ2X/eCU9YDZeGuWmxzIHvkuMj8FfX8cK/ 2m437UA877eqmcgiEy/3B7XeHUipOL83gjfq4ETzVmxVswkVvZvR6j2blQVr+MhCZPq83Ota xNB7QptPxJuNRZ49gtT6uQkyGI+2daXqkj/Mot5tKxNKtM1Vbr/3b+AEMA7qLz7QjhgGJcie qp4b0gELjY1Oe9dBAXMiDwARAQABiQI8BBgBCAAmFiEEcM/SHOJt5ePBD8hO5T0WKDGD1rMF Alg2+xACGwwFCQlmAYAACgkQ5T0WKDGD1rOYSw/+P6fYSZjTJDAl9XNfXRjRRyJSfaw6N1pA Ahuu0MIa3djFRuFCrAHUaaFZf5V2iW5xhGnrhDwE1Ksf7tlstSne/G0a+Ef7vhUyeTn6U/0m +/BrsCsBUXhqeNuraGUtaleatQijXfuemUwgB+mE3B0SobE601XLo6MYIhPh8MG32MKO5kOY hB5jzyor7WoN3ETVNQoGgMzPVWIRElwpcXr+yGoTLAOpG7nkAUBBj9n9TPpSdt/npfok9ZfL /Q+ranrxb2Cy4tvOPxeVfR58XveX85ICrW9VHPVq9sJf/a24bMm6+qEg1V/G7u/AM3fM8U2m tdrTqOrfxklZ7beppGKzC1/WLrcr072vrdiN0icyOHQlfWmaPv0pUnW3AwtiMYngT96BevfA qlwaymjPTvH+cTXScnbydfOQW8220JQwykUe+sHRZfAF5TS2YCkQvsyf7vIpSqo/ttDk4+xc Z/wsLiWTgKlih2QYULvW61XU+mWsK8+ZlYUrRMpkauN4CJ5yTpvp+Orcz5KixHQmc5tbkLWf x0n1QFc1xxJhbzN+r9djSGGN/5IBDfUqSANC8cWzHpWaHmSuU3JSAMB/N+yQjIad2ztTckZY pwT6oxng29LzZspTYUEzMz3wK2jQHw+U66qBFk8whA7B2uAU1QdGyPgahLYSOa4XAEGb6wbI FEE= Message-ID: <516df5d7-b514-11dc-130e-f1a2edce0108@web.de> Date: Thu, 16 Apr 2020 08:14:07 +0200 User-Agent: Mozilla/5.0 (X11; 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-Spam-Flag: NO 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org =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