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Wed, 16 Aug 2023 15:12:59 +0000 Date: Wed, 16 Aug 2023 08:12:56 -0700 From: Dan Williams To: Tom Lendacky , Dan Williams , CC: Kuppuswamy Sathyanarayanan , Dionna Amalie Glaze , James Bottomley , Peter Gonda , Greg Kroah-Hartman , Samuel Ortiz , , , Subject: Re: [PATCH v2 2/5] tsm: Introduce a shared ABI for attestation reports Message-ID: <64dce778240af_5ea6e29419@dwillia2-xfh.jf.intel.com.notmuch> References: <169199898909.1782217.10899362240465838600.stgit@dwillia2-xfh.jf.intel.com> <169199900110.1782217.12112722316618515086.stgit@dwillia2-xfh.jf.intel.com> <7fada981-bc73-774e-bff3-e9be56c52b66@amd.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <7fada981-bc73-774e-bff3-e9be56c52b66@amd.com> X-ClientProxiedBy: MW4PR03CA0064.namprd03.prod.outlook.com (2603:10b6:303:b6::9) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR11MB8107:EE_|SA0PR11MB4751:EE_ X-MS-Office365-Filtering-Correlation-Id: 035dd71b-c0d4-442a-011c-08db9e6b46e1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?+n8wL3mfiLr+2Z+8VlhnesO8qlraIdKiEi9e9XmXCrFPWqieDAyWI61o6BrJ?= =?us-ascii?Q?D5QDRJKnx8BeQhRI34wyA4VSGrk2ct7Es/uQuHgENAZFATMwMydswcb2TplB?= =?us-ascii?Q?1xVkYJWScD0xr7xS9UyHYM/1LR5oM3CfKhDO/Kb9ZgyRw3+A0FrbM47x0Zpe?= =?us-ascii?Q?HWYc1zPK9cFMuDr3q2FTWGWBnf4MnL97jnZZkyiQX2p+pvKMQq4ozpZEqJe+?= =?us-ascii?Q?/fu7Bchuk81TQfyZvrZwC2t+J+KGn7GFS24EuC9q1WPQJdp2TEFdKaB1l2hc?= =?us-ascii?Q?4OpaLDe4lWlWRubAuE98fblOzi3xyC8Wv2T2HHIhJdWBEdJL0KtigK6lU1p7?= =?us-ascii?Q?oxgW8Lkj62ce5EUO/RJcGOYTiNgsq9h1VrVPskFOV/DILEQBQMRqOPbrVQgj?= =?us-ascii?Q?n2wGJesndaMUNjflVpxDISSSOlDhP2y8GY/PJxIXqN1DBNca9ik36Z5D4X0h?= =?us-ascii?Q?jXiY3uOeWxc9mLWzlavFLTGuLvoAccFmDi+PGEWZok+0vj9qlrui4BO75oyG?= =?us-ascii?Q?4BSDvxYMRHRNnMWAaa86FZr3V6XE5XIw02Ti6IDLjAZhvlTpp3hi8E00+ur8?= =?us-ascii?Q?djj3A4gpGcSXR1mH8Bo8wrE4jCIzUNwHBOtlZI5TKNhvjE5SgKUhsOdwgPTQ?= =?us-ascii?Q?uGxzPQIUIX2l9Bc6fPWRRz///wnXnHJKoteaCkr4S2NHcqvT8pWD+IwKxMdb?= =?us-ascii?Q?tAiR8p45WjznSjuSx9o9jFoqHnJCkDfPZXrFMqETyt4kiQuX7OzJh1WBiTT7?= =?us-ascii?Q?ELDkSOt4THTXmbbbOX0Vm3jfbtQ5CmwnBy4dmpN5mNLLAaeBGOmXRwsiRAQR?= =?us-ascii?Q?1/N0uRdYn22ecJx+0ycsI9G94M+KOzIcqcrsfgpwzloH/31jOgoFq41ZqWX8?= =?us-ascii?Q?ajouCjLkRDx4VZu26AFlF8tPT4VawjFWIuj28lrGGxX0O0AvB/kLbnWxXcWf?= =?us-ascii?Q?OCHM5uc//usmPZlp2pVn/t/LWZ5jTPrP+oIWyYYkOj/3O4fDbrwtEDNRz9+K?= =?us-ascii?Q?HfGxvFiY7ZeIkS71F+O/diX7EhF9CYFXXcm9tFqyDzp/Bk6BhNy9ted2rlC9?= =?us-ascii?Q?azzWDe046VGTZhR50/G3BV+/tV7mNM2SqFsWJB362gjpUXizpI54CPRHokzD?= =?us-ascii?Q?c8Oor8Ev2e4vl6uygiIy8+OSy1PcVe/1wfYokUd6VFrPaaFws+ujdM6wcbdB?= =?us-ascii?Q?4s1gwF+MFpEGncmOqr0m75CknjwmqH8H92NqGoKtdnGWSqlxVICKwhdwXgbu?= =?us-ascii?Q?gwRU0jNpiTDN4T2fcPoRiulUGdgY5zazovmuagujqF/FGIXZD5h2o+NrZOHr?= =?us-ascii?Q?ojeY1abzPWy1jyeSMthFMZgzYOv4guTJbHm16Mfusmvh7ahWye3Nvgdqhdn7?= =?us-ascii?Q?FAm+AHoRo0gz1Ha8AGLjYmaQ1B1WtP4IsGO/QdsT8vb2iavVDcB8mu4tALDn?= =?us-ascii?Q?cjibLrxDthYECbMqd9WoSztcf/KZKZeV5pHKFip+qY7/ubXh5BCg6+eYU2nM?= =?us-ascii?Q?3aZJNnSDbWw81UhiCqiFapIDZMfdQOp26k8tmGyRfYVp5SfGlrCx2GBiajeF?= =?us-ascii?Q?2EyyxTDbJk/d0AqZp1fTq+uPWKmXcOuq8DjWG99z8GDQnxGVlc36uLJ/aKU1?= =?us-ascii?Q?DA=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 035dd71b-c0d4-442a-011c-08db9e6b46e1 X-MS-Exchange-CrossTenant-AuthSource: PH8PR11MB8107.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Aug 2023 15:12:59.2975 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: YGpS5fzntiozdzxLBWRKyvt11fYiDInmF1RswuGW4jIA9lefKQhaaE3zg4UzYeSZwjMR7NM1XLi/BljTiVhK/yqNPfqPukOteNNPDh0t94o= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR11MB4751 X-OriginatorOrg: intel.com Tom Lendacky wrote: > > +static ssize_t privlevel_store(struct device *dev, > > + struct device_attribute *attr, const char *buf, > > + size_t len) > > +{ > > + unsigned int val; > > + int rc; > > + > > + rc = kstrtouint(buf, 0, &val); > > + if (rc) > > + return rc; > > + > > + guard(rwsem_write)(&tsm_rwsem); > > + if (tsm_report.desc.privlevel == val) > > + return len; > > + tsm_report.desc.privlevel = val; > > + tsm_report.write_generation++; > > So I'm wondering if this use of write_generation helps or not. Since it > isn't incremented if the levels are the same, that might present race > conditions. > > What if user A requests vmpl 2 and privlevel is already 2, then > write_generation is not incremented. But before user A can read back the > generation value user B can request vmpl 3 and cause write_generation to > be incremented. > > This may not be a problem for VMPL, since that can be checked in the > returned attestation report, but it could be for the report format. If the > extended format is requested but changed to default, then the additional > certs might not be returned and the guest may think there aren't any...? > > Maybe incrementing the write_generation no matter what is best. True, and good eye. If write_generation does not always increment once per write there is no way to assume the state of the parameters. Will fix.