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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 19153C433ED for ; Wed, 5 May 2021 17:33:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7E950608FE for ; Wed, 5 May 2021 17:33:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E950608FE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 01E0F6B006E; Wed, 5 May 2021 13:33:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F11236B0070; Wed, 5 May 2021 13:33:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DD8616B0071; Wed, 5 May 2021 13:33:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0252.hostedemail.com [216.40.44.252]) by kanga.kvack.org (Postfix) with ESMTP id BB5026B006E for ; Wed, 5 May 2021 13:33:38 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D2F2252AC for ; Wed, 5 May 2021 17:33:37 +0000 (UTC) X-FDA: 78107874474.10.E71DF7A Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf08.hostedemail.com (Postfix) with ESMTP id 8BE6580192F1 for ; Wed, 5 May 2021 17:33:12 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 09265AD8A; Wed, 5 May 2021 17:33:36 +0000 (UTC) Subject: Re: [PATCH v9 08/96] mm: Fix struct page layout on 32-bit systems To: "Matthew Wilcox (Oracle)" , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Ilias Apalodimas , Jesper Dangaard Brouer References: <20210505150628.111735-1-willy@infradead.org> <20210505150628.111735-9-willy@infradead.org> From: Vlastimil Babka Message-ID: Date: Wed, 5 May 2021 19:33:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210505150628.111735-9-willy@infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Authentication-Results: imf08.hostedemail.com; dkim=none; spf=pass (imf08.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8BE6580192F1 X-Stat-Signature: tai9t3dn5iaynnt5ycrcou6kk1c6hjoj Received-SPF: none (suse.cz>: No applicable sender policy available) receiver=imf08; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: none/none X-HE-Tag: 1620235992-309425 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 5/5/21 5:05 PM, Matthew Wilcox (Oracle) wrote: > 32-bit architectures which expect 8-byte alignment for 8-byte integers > and need 64-bit DMA addresses (arm, mips, ppc) had their struct page > inadvertently expanded in 2019. When the dma_addr_t was added, it forced > the alignment of the union to 8 bytes, which inserted a 4 byte gap between > 'flags' and the union. > > Fix this by storing the dma_addr_t in one or two adjacent unsigned longs. > This restores the alignment to that of an unsigned long. We always > store the low bits in the first word to prevent the PageTail bit from > being inadvertently set on a big endian platform. If that happened, > get_user_pages_fast() racing against a page which was freed and > reallocated to the page_pool could dereference a bogus compound_head(), > which would be hard to trace back to this cause. > > Fixes: c25fff7171be ("mm: add dma_addr_t to struct page") > Signed-off-by: Matthew Wilcox (Oracle) > Acked-by: Ilias Apalodimas > Acked-by: Jesper Dangaard Brouer Acked-by: Vlastimil Babka