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Mon, 10 Nov 2025 21:13:13 -0800 From: Nicolin Chen To: , , , , , CC: , , , , , , , , , , , , , , Subject: [PATCH v5 1/5] iommu: Lock group->mutex in iommu_deferred_attach() Date: Mon, 10 Nov 2025 21:12:51 -0800 Message-ID: <11b3ab833d717feb41ce23ae6ebdc3af13ea55a7.1762835355.git.nicolinc@nvidia.com> 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: DS3PEPF0000C381:EE_|SN7PR12MB7883:EE_ X-MS-Office365-Filtering-Correlation-Id: 967611e0-4ea0-45f8-0447-08de20e1097d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|82310400026|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?nrTeELvhBSRe2R2/trtVaVvZUgapDmtJzP6dI+2c4UGJEOkdzm9OY/tV974R?= =?us-ascii?Q?TT7Mhm9/qhrXJbGCMzTpKcjbshVpz2fZELH+G5tjlCcsCPXOg1zNJ6nTXtUI?= =?us-ascii?Q?nj2I/7g2fbcKCXwqCD4YxsC9clfoVjC3yXsr7naF0gQ2qK1UkYozeih25bwm?= =?us-ascii?Q?Oi59moPx5xpTGX2aFNBHF27e5V8MtWQumwIrOzfAq9wk/qX3YBPTs07aD4fO?= =?us-ascii?Q?YD2FKDsV0Zl5qVXLlXOuS2QmeWLmzJmdNelAYTs2UUxPl8ppTat/fu1mvNFr?= =?us-ascii?Q?orQS3zXoMW6KCJ28L/++oqUDn7lbTmHIfU8GR996zZApLIB61G/7asw1PPJl?= =?us-ascii?Q?IKLX4gHDwJKFfjIglybr/T02yo7RUeH3uUowJh0ziAweDUMKEhtwtOje7iPn?= =?us-ascii?Q?NJ3xjHNYdEw4m79dgDuPhhoArBuhCMCyFQCZtwNOXw1GXe5DxBJeA/rxKtpM?= =?us-ascii?Q?bjInTvo93lx+qIy1VODFwfv5SA9SK00BQZ2A7Zp0Ys2Ry4lC05rg7a59m1ju?= =?us-ascii?Q?/jwAyQWAfyQGtng093XH+MkCO7a83nv7nECzKZjqi1/yKh1BdVTurmkDfy+o?= =?us-ascii?Q?nQQiNdeSPMLlBx970vCGV/CQOvYqgxjt523PR+5yunSIzu09ZT8DJLz+vDPx?= =?us-ascii?Q?8mhIy1BoPpIzgMrYbzJVzwGI8UsFbGgC+NXz/VVmJHpYW8FtEOhe1BI2Wqha?= =?us-ascii?Q?YrPmdi6J5i9oNL9KJsizkfkVl79GpxT+1A4kp1CivXx0W/rEAkwnrUXJqyOt?= =?us-ascii?Q?XcuqwWKKcsUDuxzNzXJlYkNFblYJH8sFYkP+bCIVol9ety68UnCxpSu3abDy?= =?us-ascii?Q?oR95UGdFoJgtPLcR8TORoi0/A7SYo1b15ztAQn1Hx7R0oJPQsw8pFCUiS2LY?= =?us-ascii?Q?D4NAkUwkvnp5BDhPpUtyn79YMSBNVY5XfihIpk9YAf4l/YOpB6Mh9dDcuT+d?= =?us-ascii?Q?cPtOKE2oFXp2dbuy+p2RqwORIh42mVxlMesL0gDP4feWb83B0P37P53Xd8QJ?= =?us-ascii?Q?s2hfC91ON6QtqGpnv8H8mtyBkJm7FIyhNgzXrafmE0gKTYBWU+jxaTCOZrpM?= =?us-ascii?Q?X/KP11LD1IBiR/u5XlQx+iNXUVFfnHK/VjLPTTeItEeSoEKzxeezPTXrmjuU?= =?us-ascii?Q?LJlhuZQGyfwrJFJHk4nOXtLmVX33PLaF0iGqPbzQ+MDvXamhRGzOfvjU2w6a?= =?us-ascii?Q?DqwBE5hiwuxhYeH6JUQS9E6V0aX1Jmq7S8VJQBUdBjNdwLlehp234hxuwwSF?= =?us-ascii?Q?lsYD0lzWbqSSkqoB+Tu1LxgpkgQF1Bc+wNF93zFAuydPxKfc1UetRzB3KlwT?= =?us-ascii?Q?ubvpl1h0QWB+VZukB9Zik0Fa2Axz6UTAHWPueycBPc/wS5GTfxULhn4vsWWj?= =?us-ascii?Q?hM7A3rHoIqLYw+d/bu4xjb/qG33cnTGUCRrBiLBpPr7w03l3+6lW0HpdCzjW?= =?us-ascii?Q?LRydRILzaIq0L5vUbkS+80KJeEXanTTskJEY2bcpTS2yHJBES/PntFVSZ+hj?= =?us-ascii?Q?NOKyiHBzJZGs8NtpcPnHbbwp2udymVSiX0M8HSsOG7NJRewCvhSQzjYRewL+?= =?us-ascii?Q?TEJ76WClS1nv9svvnCg=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(1800799024)(7416014)(376014)(82310400026)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Nov 2025 05:13:23.0674 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 967611e0-4ea0-45f8-0447-08de20e1097d X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF0000C381.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB7883 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 Signed-off-by: Nicolin Chen --- 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 2ca990dfbb884..170e522b5bda4 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