{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-21809", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-29T08:45:45.772Z", "datePublished": "2025-02-27T20:01:00.969Z", "dateUpdated": "2026-08-05T11:54:36.772Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:54:36.772Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc, afs: Fix peer hash locking vs RCU callback\n\nIn its address list, afs now retains pointers to and refs on one or more\nrxrpc_peer objects. The address list is freed under RCU and at this time,\nit puts the refs on those peers.\n\nNow, when an rxrpc_peer object runs out of refs, it gets removed from the\npeer hash table and, for that, rxrpc has to take a spinlock. However, it\nis now being called from afs's RCU cleanup, which takes place in BH\ncontext - but it is just taking an ordinary spinlock.\n\nThe put may also be called from non-BH context, and so there exists the\npossibility of deadlock if the BH-based RCU cleanup happens whilst the hash\nspinlock is held. This led to the attached lockdep complaint.\n\nFix this by changing spinlocks of rxnet->peer_hash_lock back to\nBH-disabling locks.\n\n ================================\n WARNING: inconsistent lock state\n 6.13.0-rc5-build2+ #1223 Tainted: G E\n --------------------------------\n inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.\n swapper/1/0 [HC0[0]:SC1[1]:HE1:SE0] takes:\n ffff88810babe228 (&rxnet->peer_hash_lock){+.?.}-{3:3}, at: rxrpc_put_peer+0xcb/0x180\n {SOFTIRQ-ON-W} state was registered at:\n mark_usage+0x164/0x180\n __lock_acquire+0x544/0x990\n lock_acquire.part.0+0x103/0x280\n _raw_spin_lock+0x2f/0x40\n rxrpc_peer_keepalive_worker+0x144/0x440\n process_one_work+0x486/0x7c0\n process_scheduled_works+0x73/0x90\n worker_thread+0x1c8/0x2a0\n kthread+0x19b/0x1b0\n ret_from_fork+0x24/0x40\n ret_from_fork_asm+0x1a/0x30\n irq event stamp: 972402\n hardirqs last enabled at (972402): [] _raw_spin_unlock_irqrestore+0x2e/0x50\n hardirqs last disabled at (972401): [] _raw_spin_lock_irqsave+0x18/0x60\n softirqs last enabled at (972300): [] handle_softirqs+0x3ee/0x430\n softirqs last disabled at (972313): [] __irq_exit_rcu+0x44/0x110\n\n other info that might help us debug this:\n Possible unsafe locking scenario:\n CPU0\n ----\n lock(&rxnet->peer_hash_lock);\n \n lock(&rxnet->peer_hash_lock);\n\n *** DEADLOCK ***\n 1 lock held by swapper/1/0:\n #0: ffffffff83576be0 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire+0x7/0x30\n\n stack backtrace:\n CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G E 6.13.0-rc5-build2+ #1223\n Tainted: [E]=UNSIGNED_MODULE\n Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014\n Call Trace:\n \n dump_stack_lvl+0x57/0x80\n print_usage_bug.part.0+0x227/0x240\n valid_state+0x53/0x70\n mark_lock_irq+0xa5/0x2f0\n mark_lock+0xf7/0x170\n mark_usage+0xe1/0x180\n __lock_acquire+0x544/0x990\n lock_acquire.part.0+0x103/0x280\n _raw_spin_lock+0x2f/0x40\n rxrpc_put_peer+0xcb/0x180\n afs_free_addrlist+0x46/0x90 [kafs]\n rcu_do_batch+0x2d2/0x640\n rcu_core+0x2f7/0x350\n handle_softirqs+0x1ee/0x430\n __irq_exit_rcu+0x44/0x110\n irq_exit_rcu+0xa/0x30\n sysvec_apic_timer_interrupt+0x7f/0xa0\n " } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - rxrpc is a UDP network protocol; the vulnerable `spin_lock(&rxnet->peer_hash_lock)` in `rxrpc_new_incoming_peer()` is executed by the io_thread directly in response to packets received on the AFS callback-manager port (UDP 7001), and the softirq side is driven by address-list churn parsed from remote VL/fileserver responses. Both sides of the deadlock are reachable and rate-controllable from off-host network traffic.\nAC:L - The attacker controls both sides of the timing window — flooding spoofed-source rxrpc DATA packets forces unbounded process-context acquisitions of `peer_hash_lock` with softirqs enabled, while attacker-influenced address-list churn queues `afs_free_addrlist` RCU callbacks that take the same lock from `RCU_SOFTIRQ`. At attacker-chosen packet rates the softirq reliably lands on a CPU holding the lock.\nPR:N - `rxrpc_new_incoming_call()` builds the peer object and takes the hash lock before any rxrpc security challenge is issued (`RXRPC_CONN_SERVICE_UNSECURED` → `CHALLENGING` is set afterwards), so no credentials or prior authentication are needed to reach the lock acquisition.\nUI:N - No victim action is required; an AFS client with the kafs module in use processes the attacker's packets and its own RCU address-list frees automatically.\nS:U - The deadlock wedges the kernel that owns the vulnerable code; no security boundary such as a VM, IOMMU, or sandbox is crossed.\nC:N - The defect is a lock-context inversion with no out-of-bounds access, no use-after-free, and no leakage of kernel memory or pointers to the attacker.\nI:N - No memory is corrupted and no data is modified — the fix only converts `spin_lock()` to `spin_lock_bh()` on `peer_hash_lock`, with no change to any data manipulation.\nA:H - A softirq spinning on a lock held by the interrupted process context on the same CPU is an unrecoverable self-deadlock that permanently wedges that CPU while holding `peer_hash_lock`, cascading to every other CPU doing rxrpc packet input, `sendmsg`, or peer teardown, resulting in a hard lockup/system hang." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/rxrpc/peer_event.c", "net/rxrpc/peer_object.c" ], "versions": [ { "version": "72904d7b9bfbf2dd146254edea93958bc35bbbfe", "lessThan": "10ba5a3d57af20e494e0d979d1894260989235dd", "status": "affected", "versionType": "git" }, { "version": "72904d7b9bfbf2dd146254edea93958bc35bbbfe", "lessThan": "0e77dd41689637ac4e1b8fe0f27541f373640855", "status": "affected", "versionType": "git" }, { "version": "72904d7b9bfbf2dd146254edea93958bc35bbbfe", "lessThan": "79d458c13056559d49b5e41fbc4b6890e68cf65b", "status": "affected", "versionType": "git" }, { "version": "056fc740be000d39a7dba700a935f3bbfbc664e6", "status": "affected", "versionType": "git" }, { "version": "6.7.3", "lessThan": "6.8", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/rxrpc/peer_event.c", "net/rxrpc/peer_object.c" ], "versions": [ { "version": "6.8", "status": "affected" }, { "version": "0", "lessThan": "6.8", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.13", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.13.2", "lessThanOrEqual": "6.13.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.14", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8", "versionEndExcluding": "6.12.13" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8", "versionEndExcluding": "6.13.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8", "versionEndExcluding": "6.14" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/10ba5a3d57af20e494e0d979d1894260989235dd" }, { "url": "https://git.kernel.org/stable/c/0e77dd41689637ac4e1b8fe0f27541f373640855" }, { "url": "https://git.kernel.org/stable/c/79d458c13056559d49b5e41fbc4b6890e68cf65b" } ], "title": "rxrpc, afs: Fix peer hash locking vs RCU callback", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "cvssV3_1": { "scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE" } }, { "other": { "type": "ssvc", "content": { "id": "CVE-2025-21809", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2025-10-01T19:28:41.037357Z" } } } ], "problemTypes": [ { "descriptions": [ { "lang": "en", "type": "CWE", "cweId": "CWE-667", "description": "CWE-667 Improper Locking" } ] } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-10-01T19:36:38.646Z" } } ] } }