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Mon, 15 Dec 2025 13:42:28 -0800 From: Nicolin Chen To: CC: , , , , , , , , , , , , , , , , , , , Subject: [PATCH v8 1/5] iommu: Lock group->mutex in iommu_deferred_attach() Date: Mon, 15 Dec 2025 13:42:16 -0800 Message-ID: X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH1PEPF0000AD7B:EE_|DS0PR12MB9321:EE_ X-MS-Office365-Filtering-Correlation-Id: 09fd4fad-a020-45ad-1ed2-08de3c22e295 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|7416014|376014|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?XqOQfS3J/VzuTm4BkZOOfdIBBk4UN20Q03DJqOXprvOq17xo4NShSKkKmM36?= =?us-ascii?Q?CK5Tm8u7o0hA9DRWb02tLuaZY8Q8AYAgZGMddWiU3uCQfffUHe62hORdim5N?= =?us-ascii?Q?SIMg9jv48Ykvg8C48QigZmnoDKOn0mppawvRINoSiqnyLycYeY+DRThWFjkO?= =?us-ascii?Q?0AiyOk5QUjEJXbRPBGkUZqguFmGTG+e9GmcXObo4FwC67inKYL1oWTQHnhk4?= =?us-ascii?Q?LIJY/+4Z1eDdtbTVaPnomyLC9gW9DLgeO9GoxAEY4+MyLbj+rnQ3GIFpOfCF?= =?us-ascii?Q?XJNHQko+OMvMj3J7/5V22/of8A3LcUxqpjhxOD5vAi02rEOn4/0VtVmDCxnL?= =?us-ascii?Q?WZ+T3w4UAB6ckW8bj/fBj45B/ConFdZjfnZD8ufG6iGdUDSA8+1Ya+hXQjIW?= =?us-ascii?Q?eZLjQJ+I4Xk5Bru7IMMnmTPqEW9zFtk4FjL+jhgNpEndMdmTVO+2SyVJacmI?= =?us-ascii?Q?o1lAasVLeBWrs8T/xbFuWLu95RRvHB+qSMcv5ZEiya682EtypnMhM4s5GKYB?= =?us-ascii?Q?a7nhj/cmrjFQEJ1ZMIr2t3ceuRZDL4e5R7PgUmGH70qMoDf8iI9OgFC4dTnU?= =?us-ascii?Q?D+osmG746x1nQh+pgLyvKsB922j6N2n26MZUG71aTZ/jf/NJ/ac3R+oDkbie?= =?us-ascii?Q?JHkmD9WS8ojaZ7DNCFFA1qX5yx8Hf86f1xnky9soJGEKRowVygZrC0XxH+j4?= =?us-ascii?Q?CMfIhNWmn9ah2rNFRrW0QyMItnpgVGMq21+Nnb+yo0AcKjdUFnEcnZjq3i/K?= =?us-ascii?Q?hQeNPASEYWUmo+pAmbd2UNWYA2rrsGenA4Y5mvqNEIfElxgTH58C3mM17v/T?= =?us-ascii?Q?KJDPkwajzN9/mSJdAn6I9SfTYFenO3X2zVLUFO95n+9avTJBsR5hvMF5Ikhm?= =?us-ascii?Q?bbSuDUG4a1cKeSZsLW/wSbsUTrV7xWklma1+joRCG4+5j4BBCZ8qeMF9ci/G?= =?us-ascii?Q?DjQUwb1rTBXuiobW75nLPSWXDRByeeb3YKzWYTnejmEtgjZCZGuUaaWws7FH?= =?us-ascii?Q?L6chPnptDxyfLmNRmJulzpps2UemgTb0pjbMdI+S598NZp2M2V3EduMqeu60?= =?us-ascii?Q?OvNKgsritwU7zh7s+W2LjPvoXIMk4n6Zzv4zQyiEYqfLMvYM6OQ97cZVnS2x?= =?us-ascii?Q?DHQSqbQv8lwwR0ymkBCpyzSRPE/M2MmgXeC10Mtze6m69TntGrAHLkID3+8D?= =?us-ascii?Q?+nVnIKx9bwd+W89FiICbW9SoqOHwoCTtVQF1EIc+6fLi8D2GLE0JUb5T4UTe?= =?us-ascii?Q?3st4vC7uxUdsV7YlLrCMIVvUQFaJdi8ph2PbOx9EsdOh5XAd4zdFTIALnmPF?= =?us-ascii?Q?eoz/OphZ//IibOQ6HOhGoJ2IoJ/DDjvw81iIdBkIbPWuFfn2XgRgN4RAoP6S?= =?us-ascii?Q?AL2qfzHZi/EYFLpn95EQBooiNEtp3SZfNiV6RaFaANOCXiu7xVVWslMTEz4x?= =?us-ascii?Q?+hyyI+Zw5ux68kMwWZskulY11aCg7TYGYBbVbMPcoDzFDdNI0gmUyCwp+SYq?= =?us-ascii?Q?kGtgIlJ3l2L29ss8QYORVQdlhec9vQbei5sAZ2imwfJdhm/3sHybMtmz6Rxb?= =?us-ascii?Q?a54HzYH/mhM5JxRFO9Q=3D?= X-Forefront-Antispam-Report: CIP:216.228.118.232;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge1.nvidia.com;CAT:NONE;SFS:(13230040)(1800799024)(82310400026)(7416014)(376014)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Dec 2025 21:42:45.9629 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 09fd4fad-a020-45ad-1ed2-08de3c22e295 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CH1PEPF0000AD7B.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB9321 Content-Type: text/plain; charset="utf-8" The iommu_deferred_attach() function invokes __iommu_attach_device(), but doesn't hold the group->mutex like other __iommu_attach_device() callers. Though there is no pratical bug being triggered so far, it would be better to apply the same locking to this __iommu_attach_device(), since the IOMMU drivers nowaday are more aware of the group->mutex -- some of them use the iommu_group_mutex_assert() function that could be potentially in the path of an attach_dev callback function invoked by the __iommu_attach_device(). Worth mentioning that the iommu_deferred_attach() will soon need to check group->resetting_domain that must be locked also. Thus, grab the mutex to guard __iommu_attach_device() like other callers. Reviewed-by: Jason Gunthorpe Reviewed-by: Kevin Tian Reviewed-by: Lu Baolu Tested-by: Dheeraj Kumar Srivastava Signed-off-by: Nicolin Chen Reviewed-by: Samiullah Khawaja --- drivers/iommu/iommu.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 2ca990dfbb88..170e522b5bda 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -2185,10 +2185,17 @@ EXPORT_SYMBOL_GPL(iommu_attach_device); =20 int iommu_deferred_attach(struct device *dev, struct iommu_domain *domain) { - if (dev->iommu && dev->iommu->attach_deferred) - return __iommu_attach_device(domain, dev, NULL); + /* + * This is called on the dma mapping fast path so avoid locking. This is + * racy, but we have an expectation that the driver will setup its DMAs + * inside probe while being single threaded to avoid racing. + */ + if (!dev->iommu || !dev->iommu->attach_deferred) + return 0; =20 - return 0; + guard(mutex)(&dev->iommu_group->mutex); + + return __iommu_attach_device(domain, dev, NULL); } =20 void iommu_detach_device(struct iommu_domain *domain, struct device *dev) --=20 2.43.0