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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11A2DC433EF for ; Mon, 7 Mar 2022 13:03:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234619AbiCGNEd (ORCPT ); Mon, 7 Mar 2022 08:04:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232482AbiCGNEc (ORCPT ); Mon, 7 Mar 2022 08:04:32 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AAEFA70CEF; Mon, 7 Mar 2022 05:03:37 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 02A4BD6E; Mon, 7 Mar 2022 05:03:37 -0800 (PST) Received: from [10.57.39.47] (unknown [10.57.39.47]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 195CE3F66F; Mon, 7 Mar 2022 05:03:34 -0800 (PST) Message-ID: <371ef3f2-883d-91ab-ed96-da8921efb465@arm.com> Date: Mon, 7 Mar 2022 13:03:28 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [BUG] crypto: ccree: driver does not handle case where cryptlen = authsize =0 Content-Language: en-GB To: Gilad Ben-Yossef Cc: Corentin Labbe , Christoph Hellwig , m.szyprowski@samsung.com, Herbert Xu , Linux Crypto Mailing List , Linux kernel mailing list , iommu@lists.linux-foundation.org References: <6cf91f43-df23-3ac9-e9b5-958d99d37422@arm.com> From: Robin Murphy In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On 2022-03-07 12:47, Gilad Ben-Yossef wrote: > On Mon, Mar 7, 2022 at 2:36 PM Robin Murphy wrote: >> >> On 2022-03-07 12:17, Gilad Ben-Yossef wrote: >>> On Mon, Mar 7, 2022 at 1:14 PM Robin Murphy wrote: >>> >>>> The "overlap" is in the sense of having more than one mapping within the >>>> same cacheline: >>>> >>>> [ 142.458120] DMA-API: add_dma_entry start P=ba79f200 N=ba79f >>>> D=ba79f200 L=10 DMA_FROM_DEVICE attrs=0 >>>> [ 142.458156] DMA-API: add_dma_entry start P=445dc010 N=445dc >>>> D=445dc010 L=10 DMA_TO_DEVICE attrs=0 >>>> [ 142.458178] sun8i-ss 1c15000.crypto: SRC 0/1/1 445dc000 len=16 bi=0 >>>> [ 142.458215] sun8i-ss 1c15000.crypto: DST 0/1/1 ba79f200 len=16 bi=0 >>>> [ 142.458234] DMA-API: add_dma_entry start P=ba79f210 N=ba79f >>>> D=ba79f210 L=10 DMA_FROM_DEVICE attrs=0 >>>> >>>> This actually illustrates exactly the reason why this is unsupportable. >>>> ba79f200 is mapped for DMA_FROM_DEVICE, therefore subsequently mapping >>>> ba79f210 for DMA_TO_DEVICE may cause the cacheline covering the range >>>> ba79f200-ba79f23f to be written back over the top of data that the >>>> device has already started to write to memory. Hello data corruption. >>>> >>>> Separate DMA mappings should be from separate memory allocations, >>>> respecting ARCH_DMA_MINALIGN. >>> >>> hmm... I know I'm missing something here, but how does this align with >>> the following from active_cacheline_insert() in kernel/dma/debug.c ? >>> >>> /* If the device is not writing memory then we don't have any >>> * concerns about the cpu consuming stale data. This mitigates >>> * legitimate usages of overlapping mappings. >>> */ >>> if (entry->direction == DMA_TO_DEVICE) >>> return 0; >> >> It's OK to have multiple mappings that are *all* DMA_TO_DEVICE, which >> looks to be the case that this check was intended to allow. However I >> think you're right that it should still actually check for conflicting >> directions between the new entry and any existing ones, otherwise it >> ends up a bit too lenient. >> >> Cheers, >> Robin. > > I understand what you are saying about why checking for conflicting > directions may be a good thing, but given that the code is as it is > right now, how are we seeing the warning for two mapping that one of > them is DMA_TO_DEVICE? Because it's the second one that isn't. The warning is triggered by adding the DMA_FROM_DEVICE entry, which *is* checked, and finds the DMA_TO_DEVICE entry already present. What's not great is that if those two mappings happened to be made in the opposite order then it would be missed entirely. Robin.