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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5654ACDB47E for ; Fri, 13 Oct 2023 04:38:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=gzwo1MUC6n6AnbCJw2XUlm2Ib6xmaNxF62ofrPSS2fc=; b=2mVZsXBZ4Pmw0zZX85Th8UK/91 ZbZSGHSNhl+7AoIyYFRGVUHT8vlo0hrPYsfUTSES7ClLbmDgGID1PQuIu2pN8LxUp2pa+SXMtNndg GeRnS5P4eoiKUePWq85WJ1sKXZCTswv/adyt8LoQy0TcfWTlzOJ29RGV7msrWD/ne83TUiR7xGE9J 56rK4eL/e4r/mNaDtTzbo/1KnEc9jGp9dGFGr3cjZAuV8E0YaT/F73RRn6qnkPdxaCu2B0MZWN20J bv/SsQ6CDsdSUDrweivTsvqMgVZUcu6Z6YGN+3o6nW2JWJPLKVjfmHpRVYcEUojDLa+0JzhYbHFcV 2arfC66Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qr9wE-002SyZ-1c; Fri, 13 Oct 2023 04:38:14 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qr9wB-002SyA-1A for linux-nvme@lists.infradead.org; Fri, 13 Oct 2023 04:38:12 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id E048D67373; Fri, 13 Oct 2023 06:38:06 +0200 (CEST) Date: Fri, 13 Oct 2023 06:38:06 +0200 From: Christoph Hellwig To: Kanchan Joshi Cc: Keith Busch , Christoph Hellwig , Kanchan Joshi , axboe@kernel.dk, sagi@grimberg.me, linux-nvme@lists.infradead.org, vincentfu@gmail.com, ankit.kumar@samsung.com, cpgs@samsung.com, stable@vger.kernel.org, Vincent Fu Subject: Re: [PATCH v3] nvme: fix memory corruption for passthrough metadata Message-ID: <20231013043806.GA5797@lst.de> References: <1891546521.01696823881551.JavaMail.epsvc@epcpadp4> <20231010074634.GA6514@lst.de> <20231011050254.GA32444@lst.de> <20231012043652.GA1368@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231012_213811_540891_9F42A02A X-CRM114-Status: GOOD ( 15.38 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Fri, Oct 13, 2023 at 07:49:19AM +0530, Kanchan Joshi wrote: > > precedent to start doing it. > In my mind, this was about dealing with the specific case when the > kernel memory is being used for device DMA. > We have just two cases: (i) separate meta buffer, and (ii) bounce > buffer for data (+metadata). > I had not planned sanity checks for user inputs for anything beyond that. > As opposed to being preventive (in all cases), it was about failing > only when we are certain that DMA will take place and it will corrupt > kernel memory. > > In the long-term, it may be possible for the path to do away with > memory copies. The checks can disappear with that. As soon as the user buffer is unaligned we need to bounce buffer, including for the data buffer.