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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 BF7A1C432BE for ; Tue, 31 Aug 2021 01:36:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 42ED060F6C for ; Tue, 31 Aug 2021 01:36:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 42ED060F6C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shutemov.name Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 7DC516B0071; Mon, 30 Aug 2021 21:36:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 78C596B0072; Mon, 30 Aug 2021 21:36:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 62C008D0001; Mon, 30 Aug 2021 21:36:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0020.hostedemail.com [216.40.44.20]) by kanga.kvack.org (Postfix) with ESMTP id 53C6B6B0071 for ; Mon, 30 Aug 2021 21:36:51 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id ED4D4253D4 for ; Tue, 31 Aug 2021 01:36:50 +0000 (UTC) X-FDA: 78533661780.07.4765C1E Received: from mail-lj1-f181.google.com (mail-lj1-f181.google.com [209.85.208.181]) by imf09.hostedemail.com (Postfix) with ESMTP id A7E003000104 for ; Tue, 31 Aug 2021 01:36:50 +0000 (UTC) Received: by mail-lj1-f181.google.com with SMTP id s12so29147047ljg.0 for ; Mon, 30 Aug 2021 18:36:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=xnMV+cZsWfOjaHj3VWcsuPRIHF9y2TCEWL2HI0kE1/o=; b=Y6CibzjZ+UpK6dvd/FFGXIMVyS96v2aD/lzSa73NSxhXd7b/PxlRNBSVfd1OUAAOuk X1SMBvUk3IXFBDmdERDVpNwG093uePj34V9jkcoVnzH2hdzKSEBfj6eLBD+gs3vwxPcs IIWf5NS1kRSPLKS+VWSickTaDt8sYOt3h2DenN9I1I2eAtMMlQQqF4n8sKXHTAqt5epl /2D/kxow7HSLJHT0MQWeU8zfHpUM8UIzavOQSazGpOvJ42l45pwBLPs8mV/ePhvPM1AO i3DJ0FPSsc8jgmYvuueK0Ww/PnuNlPeo2AyHcP3E87raM4Z7OtxkDcZ0mDUf1r/b+b1m sJtQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=xnMV+cZsWfOjaHj3VWcsuPRIHF9y2TCEWL2HI0kE1/o=; b=kBrifazwA6lwFwxSqAv51gM9k3e1OcdPT4CqaFnsmqrgztjgvWvF9VsF2J4biVK1vJ W+wvfa96cnm9WL8Ma1tFRBnSyMrVoIm0Sd3O3HlfiXdBZKsVnaGRftrhu3D5MVzX3HGv iS0WhGol4LE9CsYnsSdcPBOfJwH3YOzSjsZpTU2Dbs2Qu1C3lUwF4DAPm+V2UsasUtWe bJHpIsAKS2Nt4Amr/glk1TroarGDLyLuC4dXsAqsotMfrrSvD19RjM/yJtW4xmlhxbIx AfUGTOsEgZciNg/TtNnV7OhKaknNcUiWRUjxkBu6W88ufnHh0HAXUynK0Px5cTYRDxQB Y8Lw== X-Gm-Message-State: AOAM532ca/gxyhpjDJOngzSb/k7ar1QXTycXubzy+qW2WQNw2QhjShRK SCzz6t7ivpAtN9yfWxxzJovkBQ== X-Google-Smtp-Source: ABdhPJy6a+XmToZUbwzZ4SgCq1n3ItUotcAAKI0Jh4LLMf2O+HYNh/wCPvFlBL57URZnYSX5nnMFqQ== X-Received: by 2002:a05:651c:894:: with SMTP id d20mr22288121ljq.483.1630373808843; Mon, 30 Aug 2021 18:36:48 -0700 (PDT) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id k38sm1465539lfv.128.2021.08.30.18.36.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Aug 2021 18:36:48 -0700 (PDT) Received: by box.localdomain (Postfix, from userid 1000) id ADB63102E1B; Tue, 31 Aug 2021 04:36:47 +0300 (+03) Date: Tue, 31 Aug 2021 04:36:47 +0300 From: "Kirill A. Shutemov" To: Yafang Shao Cc: Christoph Hellwig , Andrew Morton , Linux MM , "Kirill A . Shutemov" Subject: Re: [PATCH] mm, gpu: fix error when FOLL_MLOCK an unpresent page Message-ID: <20210831013647.3ipichkrvpxmcnqc@box.shutemov.name> References: <20210829011953.9051-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=shutemov-name.20150623.gappssmtp.com header.s=20150623 header.b=Y6CibzjZ; dmarc=none; spf=none (imf09.hostedemail.com: domain of kirill@shutemov.name has no SPF policy when checking 209.85.208.181) smtp.mailfrom=kirill@shutemov.name X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: A7E003000104 X-Stat-Signature: xaxsnqt74ymieqdhkhtnauyjtkbocn88 X-HE-Tag: 1630373810-655320 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 Mon, Aug 30, 2021 at 06:55:02PM +0800, Yafang Shao wrote: > On Mon, Aug 30, 2021 at 6:08 PM Christoph Hellwig wrote: > > > > On Mon, Aug 30, 2021 at 05:12:32PM +0800, Yafang Shao wrote: > > > > Which is not a valid way to call get_user_pages. What we need to do is > > > > to reject that case. > > > > > > Do you mean below change ? > > > > Sory of. I think once touching this we should do a few more cleanups > > including making many of the flags private to gup.c. I'll try to find > > some time to post a more complete series. > > JFYI, below test case can also hit the bug I reported above. How does the bug manifests with the test case? I don't see any crash with it in my setup. Or do you mean you can hit __get_user_pages() with FOLL_MLOCK, but without FOLL_POPULATE? My guess is that you have wrong expectation from GUP: it will return a number of pages it advanced in the mapping, not number of present pages there. For your case it means that the array of pages can have gaps and it's okay. Fill the array with zeros before calling GUP and check if the entry is non-NULL before dereferencing it. > > #define _GNU_SOURCE > #include > #include > > #define LEN 4096 > > int main() > { > char *addr; > int ret; > > addr = mmap(NULL, LEN, PROT_READ|PROT_WRITE, MAP_PRIVATE | > MAP_ANON , -1, 0); > if (addr == MAP_FAILED) { > perror("mmap"); > return ret; > } > > /* > * MLOCK_ONFAULT will hit below if condition. > * if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) > * return -ENOENT; > */ > ret = mlock2(addr, LEN, MLOCK_ONFAULT); > // ret = mlock2(addr, LEN, 0); > if (ret < 0) { > perror("mlock2"); > return ret; > } > > return 0; > } > > -- > Thanks > Yafang > -- Kirill A. Shutemov