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 2BC6CC83000 for ; Wed, 29 Apr 2020 16:43:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C0C9420787 for ; Wed, 29 Apr 2020 16:43:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=web.de header.i=@web.de header.b="qAPJpIFJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0C9420787 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=web.de Authentication-Results: mail.kernel.org; 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Wed, 29 Apr 2020 16:43:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=web.de; s=dbaedf251592; t=1588178584; bh=u6deDAh7ES+ICnOxX8IAfRbiNhwow9Wm9VkG7jWeJMQ=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=qAPJpIFJ0m068bk0NSfqPuhirtGk8Im2OeBoVl1PIGSwoFfnQPsFndFQobhuPlyyY NNsFYhOcbaobrabnqlZqC+AmPfYBpx13bTEB7DuMghr86uZMI3yQPYCEE3U9o2vRPO /dM8PrLbyAiKJUai9rvKvrmYm+cnnNpJvWcDs74g= X-UI-Sender-Class: c548c8c5-30a9-4db5-a2e7-cb6cb037b8f9 Received: from [192.168.1.2] ([93.133.72.72]) by smtp.web.de (mrweb003 [213.165.67.108]) with ESMTPSA (Nemesis) id 0MarqU-1jjqFZ3CDC-00KMRk; Wed, 29 Apr 2020 18:43:03 +0200 Subject: Re: [PATCH v3] mm/slub: Fix incorrect interpretation of s->offset To: Waiman Long , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Kees Cook , Changbin Du , Matthew Wilcox , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org References: <20200429135328.26976-1-longman@redhat.com> 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: <20200429135328.26976-1-longman@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:wd3kwhLX6DwLMhulDGytN53sy45DgtwHEfXLhvkjJXm2ZRuqyJu /DRDPYshaufW+wg8qvDGJt6Rrxry3w4xL95irPXpWvBOth43Ey2AcTLWt23cH3hAGP7Bx2X /tdQWN6lfm5tOB6rFXZLYmt8YTbq4SetObF/HSl6N4ye9L0fVUlEJaJR4n3agQ4BebdmSyN JsRoTf9Z2kxGKYZjGt/EQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:E0Z8We4+zbY=:ralSufDbuJakJ81Dc+Hzuq FRHtzfgtBW/L4J8E93MQ93uDoqsdOfg/k40ou+3syYItneL1tVrFJoC+90kwgQnL46dkM6b47 pWouFzesFYVtk7zcoZZ+2TVNCGUCfE589nQxh+D85fjB+WaasTy3Klv3H0vwwDatamU4E8MhJ b0/fhAQ3wLxERlTHD8NA8PXOaM9NW91bG0SBCLAaEeNJ7yvE7ng+AfsZNqh8JilO7vH/1+aQa cJSo6MgN/s1j9vSxYTLms4G4qSL9DIzcoTLRz5K1ZLdoFo9olkBpWUqzfkYL/TFMPKs6whURQ RhEalFb/Apa3advZVBd9ULynjWgvugxURcqPmCnSMzdLJNF1pPZZppcbCVC+Lx0lbeT5kTBFC 4h2jmyeSFYhTH+PsW4AN+jq0UXcC1ezotL25ebF6arztYnQMxxATaRp7BnuioVUJGcN/RXlpC DJscTTxTwytwYMyl1hJwaMo8fQ1/LvC+dDSFaftjgMBPFcBZY/udzsbmF+Mv8O6V6Ki50kxkq khWXsILYke/GzvxtzWuR1s7ycJPlXoepgsUlG3Dum2/F1wsEyYW5Wlytr9bdiGszJU0wurB3c 4EVS8iSWQdNULKhf2TNlo4RlvX9iGeXdyO4t83TsTOsziGV5ansJ85Vt3viFVS7/cK3v6VN87 f+wrCt9qUTuvXX+9YlV4CkvXYRkVh7/+9KCdzuFFEQQlOday7aSr72z63pB6Em1HfAJU+suq2 ZzVaI5eayjDihzBfCIAz1KUEeXJPm53WvG7hpW8l3h1ZFv7d9OtMfd+nxTDcDY8Mpi/HVvOh4 7F5+2fSLPLr5zAMB9OsnPDQyXy0BJcjAMGB4ouFa9cxmE9btsE/4PmX41oJ9U6eDWJKbLQIkM +0byTondrA9HqO4bNHXoGb47vZ4ERDL7v+M0wVpJu3QBG/MGPk2OSRi4O26nrf8nhIXMyJiXy vodgRn6K9GlJ/+f8c7mYyUduC3irGJSurzhH9Nf0yTz94wt0KuLck8HoYdXtPoUXA6jNd+rR0 6GrrPnLHsz4AqerLvRORppwjNG8m6vzmOCIIV/5rdD2ZmKMNUQ6HYEr9XBFwFmDR8s9OvNhJ1 y0eesQAXBql7nz10mBzDnJsrMS/Sxm+lytiVtJgpqnAXyhqcIpLJOKKA97IuA4zBfSByfExw7 VVfnBRMoDl1wwNbGENzgwEv2+vjEUG6l/mNb6YRkRg11yjkmcpcVfvMoxWflOKEv4rb12nfGr eEaOjokPIb1MlXNHI 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: > In a couple of places in the slub memory allocator, the code uses > "s->offset" as a check to see if the free pointer is put right after the > object. That check is no longer true with commit 3202fa62fb43 ("slub: > relocate freelist pointer to middle of object"). Will any further collateral evolution become interesting? =E2=80=A6 > +++ b/mm/slub.c > @@ -551,15 +551,32 @@ static void print_section(char *level, char *text,= u8 *addr, =E2=80=A6 > +static inline unsigned int get_info_end(struct kmem_cache *s) > +{ > + if (freeptr_outside_object(s)) > + return s->inuse + sizeof(void *); > + else > + return s->inuse; > +} How do you think about the following source code variants? + return freeptr_outside_object(s) + ? s->inuse + sizeof(void *) + : s->inuse; > static struct track *get_track(struct kmem_cache *s, void *object, > enum track_item alloc) > { > struct track *p; > > - if (s->offset) > - p =3D object + s->offset + sizeof(void *); > - else > - p =3D object + s->inuse; > + p =3D object + get_info_end(s); > > return p + alloc; > } + struct track *p =3D object + get_info_end(s); return p + alloc; Regards, Markus