{"id":"CVE-2025-21876","title":"In the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Fix suspicious RCU usage\n\nCommit <d74169ceb0d2> (\"iommu/vt-d: Allocate DMAR fault interrupts\nlocally\") moved the call to enable_drhd_fault_handling() to a c…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Fix suspicious RCU usage\n\nCommit <d74169ceb0d2> (\"iommu/vt-d: Allocate DMAR fault interrupts\nlocally\") moved the call to enable_drhd_fault_handling() to a c…","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 6.10, < 6.12.18","linux_kernel >= 6.13, < 6.13.6","linux_kernel = 6.14"],"patched":["linux_kernel 6.13.6"],"published":"2025-03-27","updated":"2026-07-30","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-21876","references":[{"url":"https://git.kernel.org/stable/c/4117c72938493a77ab53cc4b8284be8fb6ec8065","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b150654f74bf0df8e6a7936d5ec51400d9ec06d8","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c603ccbe91d189849e1439134598ec567088dcec","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21876.json"},{"url":"https://access.redhat.com/security/cve/CVE-2025-21876"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2355411"},{"url":"https://www.cve.org/CVERecord?id=CVE-2025-21876"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21876"},{"url":"https://lore.kernel.org/linux-cve-announce/2025032710-CVE-2025-21876-6c2f@gregkh/T"}],"tags":["nvd","csaf","vex","red-hat","score-dispute"],"epss":0.0021,"epssPercentile":0.11523,"ingestedAt":"2026-07-30T06:53:10.648Z","cwe":["CWE-413"],"scores":{"nvd":8.8,"vendor":3.3},"slug":"CVE-2025-21876","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Fix suspicious RCU usage\n\nCommit <d74169ceb0d2> (\"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  <TASK>\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  </TASK>\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.\n\n## Affected\n\n- `linux_kernel >= 6.10, < 6.12.18`\n- `linux_kernel >= 6.13, < 6.13.6`\n- `linux_kernel = 6.14`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.13.6`\n\n## Vendor advisories\n\n- **Red Hat VEX** · Low · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-09-13 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21876.json)","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":48.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}