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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 006E5C2BC61 for ; Tue, 30 Oct 2018 14:03:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B6EB20823 for ; Tue, 30 Oct 2018 14:03:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9B6EB20823 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728069AbeJ3W4l (ORCPT ); Tue, 30 Oct 2018 18:56:41 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:44860 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727705AbeJ3W4l (ORCPT ); Tue, 30 Oct 2018 18:56:41 -0400 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 44B676AFD3A73; Tue, 30 Oct 2018 22:03:01 +0800 (CST) Received: from [127.0.0.1] (10.177.23.164) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.408.0; Tue, 30 Oct 2018 22:02:52 +0800 Subject: Re: [PATCH v2 1/1] iommu/arm-smmu-v3: eliminate a potential memory corruption on Hi16xx soc To: John Garry , Will Deacon References: <1540021014-8176-1-git-send-email-thunder.leizhen@huawei.com> <20181029175905.GC16739@arm.com> <5BD7B97A.1050408@huawei.com> <5f8866ef-41f4-424b-7fc3-240a4ae7b9f2@huawei.com> CC: Joerg Roedel , LinuxArm , linux-kernel , iommu , Robin Murphy , linux-arm-kernel From: "Leizhen (ThunderTown)" Message-ID: <5BD8648B.8050001@huawei.com> Date: Tue, 30 Oct 2018 22:02:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <5f8866ef-41f4-424b-7fc3-240a4ae7b9f2@huawei.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.23.164] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/10/30 17:26, John Garry wrote: > On 30/10/2018 01:52, Leizhen (ThunderTown) wrote: >> >> >> On 2018/10/30 1:59, Will Deacon wrote: >>> On Sat, Oct 20, 2018 at 03:36:54PM +0800, Zhen Lei wrote: >>>> The standard GITS_TRANSLATER register in ITS is only 4 bytes, but >>>> Hisilicon expands the next 4 bytes to carry some IMPDEF information. That >>>> means, total 8 bytes data will be written to MSIAddress each time. >>>> >>>> MSIAddr: |----4bytes----|----4bytes----| >>>> | MSIData | IMPDEF | >>>> >>>> There is no problem for ITS, because the next 4 bytes space is reserved >>>> in ITS. But it will overwrite the 4 bytes memory following "sync_count". >>>> It's very fortunately that the previous and the next neighbour of the >>>> "sync_count" are both aligned by 8 bytes, so no problem is met now. >>>> >>>> It's good to explicitly add a workaround: >>>> 1. Add gcc __attribute__((aligned(8))) to make sure that "sync_count" is >>>> always aligned by 8 bytes. >>>> 2. Add a "int" struct member to make sure the 4 bytes padding is always >>>> exist. >>>> >>>> There is no functional change. >>>> >>>> Signed-off-by: Zhen Lei >>>> --- >>>> drivers/iommu/arm-smmu-v3.c | 15 ++++++++++++++- >>>> 1 file changed, 14 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c >>>> index 5059d09..624fdd0 100644 >>>> --- a/drivers/iommu/arm-smmu-v3.c >>>> +++ b/drivers/iommu/arm-smmu-v3.c >>>> @@ -586,7 +586,20 @@ struct arm_smmu_device { >>>> >>>> struct arm_smmu_strtab_cfg strtab_cfg; >>>> >>>> - u32 sync_count; >>>> + /* >>>> + * The alignment and padding is required by Hi16xx of Hisilicon. > > Nit: I know that there is no functional change related to this bug which depends on the chip version, but how about "hi1620 and earlier"? hi16xx is very broad. OK, I will update it. > > Thanks > >>>> + * Because the ITS hardware on Hi16xx will truncate the MSIAddress(Here >>>> + * it's the address of "sync_count") to 8 bytes boundary first, then >>>> + * write 32 bits MSIdata at offset 0, and 32 bits IMPDEF data at offset >>>> + * 4. Without this workaround, the adjacent member maybe overwritten. >>>> + * >>>> + * |---4bytes---|---4bytes---| >>>> + * MSIAddress & (~0x7): MSIdata | IMPDEF data| >>>> + */ >>>> + struct { >>>> + u32 sync_count; >>>> + int padding; >>>> + } __attribute__((aligned(8))); >>> >>> I thought the conclusion after reviewing your original patch was to maintain >>> the union and drop the alignment directive? e.g. >>> >>> union { >>> u32 sync_count; >>> u64 padding; /* Hi16xx writes an extra 32 bits of goodness */ >>> }; >> OK, I will sent v3. >> >>> >>> Will >>> >>> . >>> >> > > > > . > -- Thanks! BestRegards