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_INVALID, DKIM_SIGNED,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 C7E0BC433DF for ; Tue, 4 Aug 2020 18:49:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 93C69206DA for ; Tue, 4 Aug 2020 18:49:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="byc9Hrex" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 93C69206DA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1B96E8D0182; Tue, 4 Aug 2020 14:49:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 169F68D0081; Tue, 4 Aug 2020 14:49:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0A5DE8D0182; Tue, 4 Aug 2020 14:49:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0038.hostedemail.com [216.40.44.38]) by kanga.kvack.org (Postfix) with ESMTP id E37D38D0081 for ; Tue, 4 Aug 2020 14:49:12 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 8738382499A8 for ; Tue, 4 Aug 2020 18:49:12 +0000 (UTC) X-FDA: 77113773744.18.cart00_0e15c2826fa8 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id CC008100EC67C for ; Tue, 4 Aug 2020 18:49:05 +0000 (UTC) X-HE-Tag: cart00_0e15c2826fa8 X-Filterd-Recvd-Size: 2508 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf22.hostedemail.com (Postfix) with ESMTP for ; Tue, 4 Aug 2020 18:49:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=73E/mUlgtoSN15laglO3/u/JfEyzExf5GRBwmq+AUvs=; b=byc9HrexFbc+YHrw8RujIt4Iww F7aqsHwj7A8t01g4IoTCt0QaaqdS/KMKP5mio4OpyrAsHubQs2kWmMSgpuKa5IEFbtDP7vohovp78 WKy4LjRLqKM4sGG3LPe4gMa6vh/CEd//oAdAP5hoISCTvm9jMOv4HtqTFOZZk1nPIZc66RY57OKz9 oxY+FxHtZGDs1SiJPnaoCK0MhapJHgWLEUn+BfiMc7U/KSwgVgAIzrIjIULA7jjPPO1P4qd5vKopF wOjoLgweZ44Rw27jhtv73Ol8+6jFPx1WLKRAJ9NbP3WSSS6AK8mVA0aJvuTXk9U/PsMcBnCApigp3 5DFn3gTQ==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1k31zc-0001hG-Nm; Tue, 04 Aug 2020 18:48:56 +0000 Date: Tue, 4 Aug 2020 19:48:56 +0100 From: Matthew Wilcox To: John Hubbard Cc: akpm@linux-foundation.org, cai@lca.pw, kirill@shutemov.name, linux-mm@kvack.org, rppt@linux.ibm.com, vbabka@suse.cz, william.kucharski@oracle.com, "Kirill A . Shutemov" Subject: Re: [PATCH] mm, dump_page: do not crash with bad compound_page() Message-ID: <20200804184856.GI23808@casper.infradead.org> References: <20200804161414.GG23808@casper.infradead.org> <20200804183943.1244828-1-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200804183943.1244828-1-jhubbard@nvidia.com> X-Rspamd-Queue-Id: CC008100EC67C X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 Tue, Aug 04, 2020 at 11:39:43AM -0700, John Hubbard wrote: > +static inline int __compound_mapcount(struct page *page) > +{ > + page = compound_head(page); > + return atomic_read(compound_mapcount_ptr(page)) + 1; > +} I'd suggest instead: static inline int head_mapcount(struct page *head) { return atomic_read(compound_mapcount_ptr(head)) + 1; } > +static inline int dump_page_compound_mapcount(struct page *page) > +{ > + if (WARN_ON_ONCE(!PageCompound(page))) > + return 0; > + return __compound_mapcount(page); > } And just dropping this ... it shouldn't be used outside mm/debug.c anyway. Thinking about it, we'll get the hint later that this is not to be trusted when the flags from the page do not include 'head'.