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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 B8372C4338F for ; Sat, 7 Aug 2021 18:41:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 254F260F42 for ; Sat, 7 Aug 2021 18:41:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 254F260F42 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 4F8AF8D0001; Sat, 7 Aug 2021 14:41:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4A8036B0071; Sat, 7 Aug 2021 14:41:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3964D8D0001; Sat, 7 Aug 2021 14:41:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0228.hostedemail.com [216.40.44.228]) by kanga.kvack.org (Postfix) with ESMTP id 1E4276B006C for ; Sat, 7 Aug 2021 14:41:17 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id C238B1CB1B for ; Sat, 7 Aug 2021 18:41:16 +0000 (UTC) X-FDA: 78449152152.08.2D27CC9 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf17.hostedemail.com (Postfix) with ESMTP id 75CDAF00839D for ; Sat, 7 Aug 2021 18:41:16 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 5DDFD60F25; Sat, 7 Aug 2021 18:41:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1628361675; bh=zvgjE7YTOv76OGelHU+WXD7jLMPH6Bf/LG1/8h+9tOM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=V+N1HZP2hATamgCS+x0xY8/o2PAoBFXVEcQWz6anC9aVDpHJv+A4HXCdNWsbjC5cS d8fj9BRGrIm6R9d0xeYoUSqYm58PB9FjWsbBVDu9kQ2MuZGE/lnlY4ND5bkvHLWZct hKRozVDKcIf6MvZvVTQYSnmShxfhHhfsfahDgtm0= Date: Sat, 7 Aug 2021 11:41:12 -0700 From: Andrew Morton To: Miaohe Lin Cc: , , , , , Subject: Re: [PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in __gup_device_huge() Message-Id: <20210807114112.6e45b31c65dd62169fee8718@linux-foundation.org> In-Reply-To: <20210807093620.21347-5-linmiaohe@huawei.com> References: <20210807093620.21347-1-linmiaohe@huawei.com> <20210807093620.21347-5-linmiaohe@huawei.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 75CDAF00839D Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=V+N1HZP2; dmarc=none; spf=pass (imf17.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Stat-Signature: y7h475h46cer1d4uqdrkmb13kqg73n35 X-HE-Tag: 1628361676-296073 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 Sat, 7 Aug 2021 17:36:19 +0800 Miaohe Lin wrote: > When failed to try_grab_page, put_dev_pagemap() is missed. So pgmap > refcnt will leak in this case. Also we remove the check for pgmap > against NULL as it's also checked inside the put_dev_pagemap(). > > ... > > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2253,14 +2253,14 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr, > pages[*nr] = page; > if (unlikely(!try_grab_page(page, flags))) { > undo_dev_pagemap(nr, nr_start, flags, pages); > + put_dev_pagemap(pgmap); > return 0; > } > (*nr)++; > pfn++; > } while (addr += PAGE_SIZE, addr != end); > > - if (pgmap) > - put_dev_pagemap(pgmap); > + put_dev_pagemap(pgmap); > return 1; > } We can simplify further, and remove the troublesome multiple return points? --- a/mm/gup.c~mm-gup-fix-potential-pgmap-refcnt-leak-in-__gup_device_huge-fix +++ a/mm/gup.c @@ -2247,14 +2247,13 @@ static int __gup_device_huge(unsigned lo pgmap = get_dev_pagemap(pfn, pgmap); if (unlikely(!pgmap)) { undo_dev_pagemap(nr, nr_start, flags, pages); - return 0; + break; } SetPageReferenced(page); pages[*nr] = page; if (unlikely(!try_grab_page(page, flags))) { undo_dev_pagemap(nr, nr_start, flags, pages); - put_dev_pagemap(pgmap); - return 0; + break; } (*nr)++; pfn++; _