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Wed, 3 Jun 2026 14:27:18 -0700 From: Nicolin Chen To: Will Deacon , Jason Gunthorpe , "Kevin Tian" CC: Robin Murphy , Joerg Roedel , "Shuah Khan" , Pranjal Shrivastava , Kees Cook , Yi Liu , Eric Auger , , , , Subject: [PATCH v1 1/4] iommufd: Set upper bounds on cache invalidation entry_num and entry_len Date: Wed, 3 Jun 2026 14:26:53 -0700 Message-ID: <447fa93663f7526eb361719e83fa8b649464483d.1780521606.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: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF0001AB55:EE_|BN5PR12MB9485:EE_ X-MS-Office365-Filtering-Correlation-Id: 2b4da638-c59a-4fb0-caf0-08dec1b6f21e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|7416014|82310400026|36860700016|56012099006|11063799006|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: LccMkQ626uEalGgjixkKMmpPqhl9FVvODL7+o/VEU6//cfC9/kkVNEUBqGZH8ay/SRThTWbYtGuhhMMJeRqoGNFDsPIWmQq01s+aaQz4w7pyJ8ri02mdnNOGQn975JbK8d4riovcQvMqOs4k/rAKGnnsWTSdhqTyz1E9ZTa07hlVInqPOIOM+y6qcYa6mL6wQdU6O8hHf+nsQRyK587QYpfp5PU1B2izVrI+oxreIvyRWSdxQ5Os33yGOEGEHoUru1PUhb+63eLOmOk+04Bq/aJ1pjB83u6qS96Gf06nW8F80qh/L233xo/4lrUaT9CZ8LlXyA7tlQ7h9PsCA0lHMun8Gsng4DUPyuSqoidzfsptLkVwEDkyr1w2y8KtjfM0BXlrDv/nSHiVH2L0CrsELd5YUaJcipYWA2ZlQ996FCVS0mshVSO9VOFFh9YuHxkP X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jun 2026 21:27:42.0935 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2b4da638-c59a-4fb0-caf0-08dec1b6f21e X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL6PEPF0001AB55.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN5PR12MB9485 iommufd_hwpt_invalidate() takes a user-controlled entry_num and entry_len, each bounded only by U32_MAX. An entry_len beyond the kernel's struct size makes the copy helper verify the extra bytes are zero, scanning that excess in one uninterruptible pass; a multi-gigabyte value over zeroed user memory trips the soft-lockup watchdog. A large entry_num is the other half, driving the backend invalidation loop with no reschedule. The VT-d nested handler, for one, copies each entry and flushes caches per iteration, pinning the CPU on a non-preemptible kernel. Cap both in the ioctl. entry_len is held under PAGE_SIZE, above any request struct, and entry_num under 1 << 19, the order of a hardware invalidation queue and well beyond any real batch, bounding the per-call loop length. Fixes: 8c6eabae3807 ("iommufd: Add IOMMU_HWPT_INVALIDATE") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Nicolin Chen --- drivers/iommu/iommufd/hw_pagetable.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c index fe789c2dc0c97..623cc608ca0cd 100644 --- a/drivers/iommu/iommufd/hw_pagetable.c +++ b/drivers/iommu/iommufd/hw_pagetable.c @@ -489,6 +489,9 @@ int iommufd_hwpt_get_dirty_bitmap(struct iommufd_ucmd *ucmd) return rc; } +/* An arbitrary entry_num cap, far above any realistic invalidation batch */ +#define IOMMU_HWPT_INVALIDATE_ENTRY_NUM_MAX (1U << 19) + int iommufd_hwpt_invalidate(struct iommufd_ucmd *ucmd) { struct iommu_hwpt_invalidate *cmd = ucmd->cmd; @@ -507,7 +510,13 @@ int iommufd_hwpt_invalidate(struct iommufd_ucmd *ucmd) goto out; } - if (cmd->entry_num && (!cmd->data_uptr || !cmd->entry_len)) { + /* + * Bound entry_num and entry_len so a single call cannot pin the CPU; + * entry_len also caps the copy_struct_from_user() trailing-zero scan. + */ + if (cmd->entry_num && + (!cmd->data_uptr || !cmd->entry_len || cmd->entry_len > PAGE_SIZE || + cmd->entry_num > IOMMU_HWPT_INVALIDATE_ENTRY_NUM_MAX)) { rc = -EINVAL; goto out; } -- 2.43.0