{"id":"CVE-2025-21876","summary":"iommu/vt-d: Fix suspicious RCU usage","details":"In the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Fix suspicious RCU usage\n\nCommit \u003cd74169ceb0d2\u003e (\"iommu/vt-d: Allocate DMAR fault interrupts\nlocally\") moved the call to enable_drhd_fault_handling() to a code\npath that does not hold any lock while traversing the drhd list. Fix\nit by ensuring the dmar_global_lock lock is held when traversing the\ndrhd list.\n\nWithout this fix, the following warning is triggered:\n =============================\n WARNING: suspicious RCU usage\n 6.14.0-rc3 #55 Not tainted\n -----------------------------\n drivers/iommu/intel/dmar.c:2046 RCU-list traversed in non-reader section!!\n               other info that might help us debug this:\n               rcu_scheduler_active = 1, debug_locks = 1\n 2 locks held by cpuhp/1/23:\n #0: ffffffff84a67c50 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x87/0x2c0\n #1: ffffffff84a6a380 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x87/0x2c0\n stack backtrace:\n CPU: 1 UID: 0 PID: 23 Comm: cpuhp/1 Not tainted 6.14.0-rc3 #55\n Call Trace:\n  \u003cTASK\u003e\n  dump_stack_lvl+0xb7/0xd0\n  lockdep_rcu_suspicious+0x159/0x1f0\n  ? __pfx_enable_drhd_fault_handling+0x10/0x10\n  enable_drhd_fault_handling+0x151/0x180\n  cpuhp_invoke_callback+0x1df/0x990\n  cpuhp_thread_fun+0x1ea/0x2c0\n  smpboot_thread_fn+0x1f5/0x2e0\n  ? __pfx_smpboot_thread_fn+0x10/0x10\n  kthread+0x12a/0x2d0\n  ? __pfx_kthread+0x10/0x10\n  ret_from_fork+0x4a/0x60\n  ? __pfx_kthread+0x10/0x10\n  ret_from_fork_asm+0x1a/0x30\n  \u003c/TASK\u003e\n\nHolding the lock in enable_drhd_fault_handling() triggers a lockdep splat\nabout a possible deadlock between dmar_global_lock and cpu_hotplug_lock.\nThis is avoided by not holding dmar_global_lock when calling\niommu_device_register(), which initiates the device probe process.","modified":"2026-04-02T12:45:15.575467Z","published":"2025-03-27T14:57:06.802Z","related":["SUSE-SU-2025:01919-1","SUSE-SU-2025:01951-1","SUSE-SU-2025:01967-1","SUSE-SU-2025:1177-1","SUSE-SU-2025:1178-1","SUSE-SU-2025:1180-1","SUSE-SU-2025:20190-1","SUSE-SU-2025:20192-1","SUSE-SU-2025:20260-1","SUSE-SU-2025:20270-1","USN-7521-2"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21876.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/4117c72938493a77ab53cc4b8284be8fb6ec8065"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b150654f74bf0df8e6a7936d5ec51400d9ec06d8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c603ccbe91d189849e1439134598ec567088dcec"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21876.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21876"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"d74169ceb0d2e32438946a2f1f9fc8c803304bd6"},{"fixed":"4117c72938493a77ab53cc4b8284be8fb6ec8065"},{"fixed":"c603ccbe91d189849e1439134598ec567088dcec"},{"fixed":"b150654f74bf0df8e6a7936d5ec51400d9ec06d8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21876.json"}}],"schema_version":"1.7.5"}