# CVE-2025-21809: linux: In the Linux kernel, the following vulnerability has been resolved: rxrpc, afs: Fix peer hash locking vs RCU callbac... CVE-2025-21809 is fixed in 36 products on 1 platform, first by DEBIAN-CVE-2025-21809, released February 27, 2025. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2025-21809 - Priority: Routine - CVSS: 5.5 (medium) - EPSS: 0.0032 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Feb 27, 2025 ## Description In the Linux kernel, the following vulnerability has been resolved: rxrpc, afs: Fix peer hash locking vs RCU callback In its address list, afs now retains pointers to and refs on one or more rxrpc_peer objects. The address list is freed under RCU and at this time, it puts the refs on those peers. Now, when an rxrpc_peer object runs out of refs, it gets removed from the peer hash table and, for that, rxrpc has to take a spinlock. However, it is now being called from afs's RCU cleanup, which takes place in BH context - but it is just taking an ordinary spinlock. The put may also be called from non-BH context, and so there exists the possibility of deadlock if the BH-based RCU cleanup happens whilst the hash spinlock is held. This led to the attached lockdep complaint. Fix this by changing spinlocks of rxnet->peer_hash_lock back to BH-disabling locks. ================================ WARNING: inconsistent lock state 6.13.0-rc5-build2+ #1223 Tainted: G E -------------------------------- inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. swapper/1/0 [HC0[0]:SC1[1]:HE1:SE0] takes: ffff88810babe228 (&rxnet->peer_hash_lock){+.?.}-{3:3}, at: rxrpc_put_peer+0xcb/0x180 {SOFTIRQ-ON-W} state was registered at: mark_usage+0x164/0x180 __lock_acquire+0x544/0x990 lock_acquire.part.0+0x103/0x280 _raw_spin_lock+0x2f/0x40 rxrpc_peer_keepalive_worker+0x144/0x440 process_one_work+0x486/0x7c0 process_scheduled_works+0x73/0x90 worker_thread+0x1c8/0x2a0 kthread+0x19b/0x1b0 ret_from_fork+0x24/0x40 ret_from_fork_asm+0x1a/0x30 irq event stamp: 972402 hardirqs last enabled at (972402): [] _raw_spin_unlock_irqrestore+0x2e/0x50 hardirqs last disabled at (972401): [] _raw_spin_lock_irqsave+0x18/0x60 softirqs last enabled at (972300): [] handle_softirqs+0x3ee/0x430 softirqs last disabled at (972313): [] __irq_exit_rcu+0x44/0x110 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&rxnet->peer_hash_lock); lock(&rxnet->peer_hash_lock); *** DEADLOCK *** 1 lock held by swapper/1/0: #0: ffffffff83576be0 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire+0x7/0x30 stack backtrace: CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G E 6.13.0-rc5-build2+ #1223 Tainted: [E]=UNSIGNED_MODULE Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: dump_stack_lvl+0x57/0x80 print_usage_bug.part.0+0x227/0x240 valid_state+0x53/0x70 mark_lock_irq+0xa5/0x2f0 mark_lock+0xf7/0x170 mark_usage+0xe1/0x180 __lock_acquire+0x544/0x990 lock_acquire.part.0+0x103/0x280 _raw_spin_lock+0x2f/0x40 rxrpc_put_peer+0xcb/0x180 afs_free_addrlist+0x46/0x90 [kafs] rcu_do_batch+0x2d2/0x640 rcu_core+0x2f7/0x350 handle_softirqs+0x1ee/0x430 __irq_exit_rcu+0x44/0x110 irq_exit_rcu+0xa/0x30 sysvec_apic_timer_interrupt+0x7f/0xa0 ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | kernel-uek ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-core ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-core ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-core ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-core ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-devel ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-devel ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-core ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-core ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-deprecated ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-deprecated ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-desktop ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-desktop ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-extra ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-extra ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-extra-netfilter ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-extra-netfilter ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-usb ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-usb ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-wireless ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-debug-modules-wireless ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-devel ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-devel ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-doc ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-doc ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-core ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-core ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-deprecated ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-deprecated ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-desktop ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-desktop ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-extra ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-extra ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-extra-netfilter ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-extra-netfilter ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-usb ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-usb ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-wireless ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-modules-wireless ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-tools ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek-tools ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-core ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-core ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-devel ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-devel ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-core ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-core ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-deprecated ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-deprecated ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-desktop ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-desktop ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-extra ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-extra ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-extra-netfilter ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-extra-netfilter ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-usb ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-usb ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-wireless ol 10 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | kernel-uek64k-modules-wireless ol 9 | 0:6.12.0-101.33.4.3.el9uek | [ELSA-2025-20480](https://patchblox.com/security/data/fix/linux/elsa-2025-20480.md) | Jul 17, 2025 | | Linux | linux Debian 13.5 (trixie) | 6.12.13-1 | [DEBIAN-CVE-2025-21809](https://patchblox.com/security/data/fix/linux/debian-cve-2025-21809.md) | Feb 27, 2025 | | Linux | linux Debian 14 | 6.12.13-1 | [DEBIAN-CVE-2025-21809](https://patchblox.com/security/data/fix/linux/debian-cve-2025-21809.md) | Feb 27, 2025 | --- Data as of 2026-11-08T19:12:23Z UTC. 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