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Tsirkin" CC: Yongji Xie , Jason Wang , Stefan Hajnoczi , virtualization , , linux-kernel References: <20210809101609.148-1-xieyongji@bytedance.com> <06af4897-7339-fca7-bdd9-e0f9c2c6195b@nvidia.com> <6d6154d7-7947-68be-4e1e-4c1d0a94b2bc@nvidia.com> <7f0181d7-ff5c-0346-66ee-1de3ed23f5dd@nvidia.com> <20210823080952-mutt-send-email-mst@kernel.org> From: Max Gurtovoy Message-ID: Date: Tue, 24 Aug 2021 01:31:10 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210823080952-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [172.20.187.6] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To DRHQMAIL107.nvidia.com (10.27.9.16) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 8ee8a483-ac08-4b6b-dc4b-08d96685b845 X-MS-TrafficTypeDiagnostic: BY5PR12MB4801: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6108; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.32;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:schybrid01.nvidia.com;CAT:NONE;SFS:(4636009)(376002)(136003)(346002)(396003)(39860400002)(46966006)(36840700001)(5660300002)(356005)(47076005)(7636003)(82740400003)(70206006)(2906002)(86362001)(316002)(82310400003)(16576012)(36860700001)(83380400001)(36756003)(31696002)(16526019)(70586007)(4326008)(26005)(8936002)(186003)(8676002)(966005)(53546011)(336012)(426003)(2616005)(478600001)(31686004)(6916009)(54906003)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Aug 2021 22:31:15.5316 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8ee8a483-ac08-4b6b-dc4b-08d96685b845 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.32];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT006.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4801 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/23/2021 3:13 PM, Michael S. Tsirkin wrote: > On Mon, Aug 23, 2021 at 01:45:31PM +0300, Max Gurtovoy wrote: >> It helpful if there is a justification for this. >> >> In this case, no such HW device exist and the only device that can cause >> this trouble today is user space VDUSE device that must be validated by the >> emulation VDUSE kernel driver. >> >> Otherwise, will can create 1000 commit like this in the virtio level (for >> example for each feature for each virtio device). > Yea, it's a lot of work but I don't think it's avoidable. > >>>>>>> And regardless of userspace device, we still need to fix it for other cases. >>>>>> which cases ? Do you know that there is a buggy HW we need to workaround ? >>>>>> >>>>> No, there isn't now. But this could be a potential attack surface if >>>>> the host doesn't trust the device. >>>> If the host doesn't trust a device, why it continues using it ? >>>> >>> IIUC this is the case for the encrypted VMs. >> what do you mean encrypted VM ? >> >> And how this small patch causes a VM to be 100% encryption supported ? >> >>>> Do you suggest we do these workarounds in all device drivers in the kernel ? >>>> >>> Isn't it the driver's job to validate some unreasonable configuration? >> The check should be in different layer. >> >> Virtio blk driver should not cover on some strange VDUSE stuff. > Yes I'm not convinced VDUSE is a valid use-case. I think that for > security and robustness it should validate data it gets from userspace > right there after reading it. > But I think this is useful for the virtio hardening thing. > https://lwn.net/Articles/865216/ I don't see how this change is assisting confidential computing. Confidential computingtalks about encrypting guest memory from the host, and not adding some quirks to devices. > > Yongji - I think the commit log should be much more explicit that > this is hardening. Otherwise people get confused and think this > needs a CVE or a backport for security. >