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=unavailable 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 A1057C432BE for ; Sat, 7 Aug 2021 18:41:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89D1360C41 for ; Sat, 7 Aug 2021 18:41:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229737AbhHGSlf (ORCPT ); Sat, 7 Aug 2021 14:41:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:33022 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229464AbhHGSle (ORCPT ); Sat, 7 Aug 2021 14:41:34 -0400 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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++; _