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7.5

Linux kernel can deadlock during AFS cleanup

CVE-2025-21809 · published 1 year ago
Summary

The AFS file system component in the Linux kernel can hold a lock while the kernel is cleaning up address lists, which may conflict with another lock used by the network code. This conflict can cause the system to hang. Updating to a kernel version that includes the fix eliminates the lock conflict and restores normal operation.

What to do
  • Update linux kernel to version 6.13.2.
  • Update canonical linux to version 6.8.0-138.138.aikido.86.
  • Update canonical rootio-linux to version 6.8.0-138.138.aikido.86.
  • Update canonical linux-aws-6.8 to version 6.8.0-1032.34~22.04.1.
  • Update canonical linux-azure-6.8 to version 6.8.0-1034.39~22.04.1.
  • Update canonical linux-gcp-6.8 to version 6.8.0-1033.35~22.04.1.
  • Update canonical linux-hwe-6.8 to version 6.8.0-64.67~22.04.1.
  • Update canonical linux-ibm-6.8 to version 6.8.0-1029.29~22.04.1.
  • Update canonical linux-lowlatency-hwe-6.8 to version 6.8.0-64.67.1~22.04.1.
  • Update canonical linux-nvidia-6.8 to version 6.8.0-1031.34~22.04.1.
  • Update canonical linux-oracle-6.8 to version 6.8.0-1029.30~22.04.1.
  • Update canonical linux-riscv-6.8 to version 6.8.0-64.67~22.04.1.
  • Update canonical linux-realtime-6.8 to version 6.8.1-1025.26~22.04.1.
  • Update canonical linux to version 6.8.0-64.67.
  • Update canonical linux-aws to version 6.8.0-1032.34.
  • Update canonical linux-azure to version 6.8.0-1034.39.
  • Update canonical linux-azure-6.11 to version 6.11.0-1015.15~24.04.1.
  • Update canonical linux-azure-nvidia to version 6.8.0-1022.23.
  • Update canonical linux-gcp to version 6.8.0-1033.35.
  • Update canonical linux-gcp-6.11 to version 6.11.0-1015.15~24.04.1.
  • Update canonical linux-gke to version 6.8.0-1028.32.
  • Update canonical linux-gkeop to version 6.8.0-1015.17.
  • Update canonical linux-hwe-6.11 to version 6.11.0-26.26~24.04.1.
  • Update canonical linux-ibm to version 6.8.0-1029.29.
  • Update canonical linux-lowlatency to version 6.8.0-64.67.1.
  • Update canonical linux-lowlatency-hwe-6.11 to version 6.11.0-1014.15~24.04.1.
  • Update canonical linux-nvidia to version 6.8.0-1031.34.
  • Update canonical linux-nvidia-6.11 to version 6.11.0-1010.10.
  • Update canonical linux-nvidia-lowlatency to version 6.8.0-1031.34.1.
  • Update canonical linux-nvidia-tegra to version 6.8.0-1008.8.
  • Update canonical linux-oem-6.11 to version 6.11.0-1022.22.
  • Update canonical linux-oem-6.8 to version 6.8.0-1031.31.
  • Update canonical linux-oracle to version 6.8.0-1029.30.
  • Update canonical linux-raspi to version 6.8.0-1031.35.
  • Update canonical linux-xilinx to version 6.8.0-1017.18.
  • Update canonical linux-raspi-realtime to version 6.8.0-2026.27.
  • Update canonical linux-realtime to version 6.8.1-1025.26.
  • Update canonical linux-fips to version 6.8.0-78.78+fips1.
  • Update linux to version 6.8.0-146.146.aikido.89.
  • Update rootio-linux to version 6.8.0-146.146.aikido.89.
  • Update linux to version 6.8.0-147.147.aikido.90.
  • Update rootio-linux to version 6.8.0-147.147.aikido.90.
  • Update linux linux to version 10ba5a3d57af20e494e0d979d1894260989235dd or later.
Affected software
Ecosystem VendorProductAffected versions
– linux linux_kernel >= 6.7.3, < 6.12.13
>= 6.13, < 6.13.2
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
– linux linux < 10ba5a3d57af20e494e0d979d1894260989235dd
6.8
Linux linux kernel >= 6.13.0, < 6.13.2
Fix: upgrade to 6.13.2
Root:Ubuntu:24.04 canonical linux < 6.8.0-138.138.aikido.86
Fix: upgrade to 6.8.0-138.138.aikido.86
Root:Ubuntu:24.04 canonical rootio-linux < 6.8.0-138.138.aikido.86
Fix: upgrade to 6.8.0-138.138.aikido.86
Ubuntu:16.04:LTS canonical linux-hwe-edge All versions
Ubuntu:18.04:LTS canonical linux-aws-5.0 All versions
Ubuntu:18.04:LTS canonical linux-aws-5.3 All versions
Ubuntu:18.04:LTS canonical linux-azure All versions
Ubuntu:18.04:LTS canonical linux-azure-5.3 All versions
Ubuntu:18.04:LTS canonical linux-azure-edge All versions
Ubuntu:18.04:LTS canonical linux-gcp All versions
Ubuntu:18.04:LTS canonical linux-gcp-5.3 All versions
Ubuntu:18.04:LTS canonical linux-gke-4.15 All versions
Ubuntu:18.04:LTS canonical linux-gke-5.4 All versions
Ubuntu:18.04:LTS canonical linux-gkeop-5.4 All versions
Ubuntu:18.04:LTS canonical linux-hwe All versions
Ubuntu:18.04:LTS canonical linux-oem All versions
Ubuntu:18.04:LTS canonical linux-oracle-5.0 All versions
Ubuntu:18.04:LTS canonical linux-oracle-5.3 All versions
Ubuntu:20.04:LTS canonical linux-aws-5.11 All versions
Ubuntu:20.04:LTS canonical linux-aws-5.13 All versions
Ubuntu:20.04:LTS canonical linux-aws-5.8 All versions
Ubuntu:20.04:LTS canonical linux-azure-5.11 All versions
Ubuntu:20.04:LTS canonical linux-azure-5.13 All versions
Ubuntu:20.04:LTS canonical linux-azure-5.8 All versions
Ubuntu:20.04:LTS canonical linux-azure-fde All versions
Ubuntu:20.04:LTS canonical linux-gcp-5.11 All versions
Ubuntu:20.04:LTS canonical linux-gcp-5.13 All versions
Ubuntu:20.04:LTS canonical linux-gcp-5.8 All versions
Ubuntu:20.04:LTS canonical linux-gke All versions
Ubuntu:20.04:LTS canonical linux-gke-5.15 All versions
Ubuntu:20.04:LTS canonical linux-gkeop All versions
Ubuntu:20.04:LTS canonical linux-gkeop-5.15 All versions
Ubuntu:20.04:LTS canonical linux-hwe-5.11 All versions
Ubuntu:20.04:LTS canonical linux-hwe-5.13 All versions
Ubuntu:20.04:LTS canonical linux-hwe-5.8 All versions
Ubuntu:20.04:LTS canonical linux-intel-5.13 All versions
Ubuntu:20.04:LTS canonical linux-oem-5.10 All versions
Ubuntu:20.04:LTS canonical linux-oem-5.13 All versions
Ubuntu:20.04:LTS canonical linux-oem-5.14 All versions
Ubuntu:20.04:LTS canonical linux-oem-5.6 All versions
Ubuntu:20.04:LTS canonical linux-oracle-5.11 All versions
Ubuntu:20.04:LTS canonical linux-oracle-5.13 All versions
Ubuntu:20.04:LTS canonical linux-oracle-5.8 All versions
Ubuntu:20.04:LTS canonical linux-raspi2 All versions
Ubuntu:20.04:LTS canonical linux-riscv All versions
Ubuntu:20.04:LTS canonical linux-riscv-5.11 All versions
Ubuntu:20.04:LTS canonical linux-riscv-5.8 All versions
Ubuntu:22.04:LTS canonical linux-allwinner-5.19 All versions
Showing 50 of 119. Show the rest
Ecosystem VendorProductAffected versions
Ubuntu:22.04:LTS canonical linux-aws-5.19 All versions
Ubuntu:22.04:LTS canonical linux-aws-6.2 All versions
Ubuntu:22.04:LTS canonical linux-aws-6.5 All versions
Ubuntu:22.04:LTS canonical linux-aws-6.8 < 6.8.0-1032.34~22.04.1
Fix: upgrade to 6.8.0-1032.34~22.04.1
Ubuntu:22.04:LTS canonical linux-azure-5.19 All versions
Ubuntu:22.04:LTS canonical linux-azure-6.2 All versions
Ubuntu:22.04:LTS canonical linux-azure-6.5 All versions
Ubuntu:22.04:LTS canonical linux-azure-6.8 < 6.8.0-1034.39~22.04.1
Fix: upgrade to 6.8.0-1034.39~22.04.1
Ubuntu:22.04:LTS canonical linux-azure-fde-5.19 All versions
Ubuntu:22.04:LTS canonical linux-azure-fde-6.2 All versions
Ubuntu:22.04:LTS canonical linux-gcp-5.19 All versions
Ubuntu:22.04:LTS canonical linux-gcp-6.2 All versions
Ubuntu:22.04:LTS canonical linux-gcp-6.5 All versions
Ubuntu:22.04:LTS canonical linux-gcp-6.8 < 6.8.0-1033.35~22.04.1
Fix: upgrade to 6.8.0-1033.35~22.04.1
Ubuntu:22.04:LTS canonical linux-hwe-5.19 All versions
Ubuntu:22.04:LTS canonical linux-hwe-6.2 All versions
Ubuntu:22.04:LTS canonical linux-hwe-6.5 All versions
Ubuntu:22.04:LTS canonical linux-hwe-6.8 < 6.8.0-64.67~22.04.1
Fix: upgrade to 6.8.0-64.67~22.04.1
Ubuntu:22.04:LTS canonical linux-ibm-6.8 < 6.8.0-1029.29~22.04.1
Fix: upgrade to 6.8.0-1029.29~22.04.1
Ubuntu:22.04:LTS canonical linux-intel-iot-realtime All versions
Ubuntu:22.04:LTS canonical linux-lowlatency-hwe-5.19 All versions
Ubuntu:22.04:LTS canonical linux-lowlatency-hwe-6.2 All versions
Ubuntu:22.04:LTS canonical linux-lowlatency-hwe-6.5 All versions
Ubuntu:22.04:LTS canonical linux-lowlatency-hwe-6.8 < 6.8.0-64.67.1~22.04.1
Fix: upgrade to 6.8.0-64.67.1~22.04.1
Ubuntu:22.04:LTS canonical linux-nvidia-6.2 All versions
Ubuntu:22.04:LTS canonical linux-nvidia-6.5 All versions
Ubuntu:22.04:LTS canonical linux-nvidia-6.8 < 6.8.0-1031.34~22.04.1
Fix: upgrade to 6.8.0-1031.34~22.04.1
Ubuntu:22.04:LTS canonical linux-oem-5.17 All versions
Ubuntu:22.04:LTS canonical linux-oem-6.0 All versions
Ubuntu:22.04:LTS canonical linux-oem-6.1 All versions
Ubuntu:22.04:LTS canonical linux-oem-6.5 All versions
Ubuntu:22.04:LTS canonical linux-oracle-6.5 All versions
Ubuntu:22.04:LTS canonical linux-oracle-6.8 < 6.8.0-1029.30~22.04.1
Fix: upgrade to 6.8.0-1029.30~22.04.1
Ubuntu:22.04:LTS canonical linux-realtime All versions
Ubuntu:22.04:LTS canonical linux-riscv-5.19 All versions
Ubuntu:22.04:LTS canonical linux-riscv-6.5 All versions
Ubuntu:22.04:LTS canonical linux-riscv-6.8 < 6.8.0-64.67~22.04.1
Fix: upgrade to 6.8.0-64.67~22.04.1
Ubuntu:22.04:LTS canonical linux-starfive-5.19 All versions
Ubuntu:22.04:LTS canonical linux-starfive-6.2 All versions
Ubuntu:22.04:LTS canonical linux-starfive-6.5 All versions
Ubuntu:Pro:Realtime:22.04:LTS canonical linux-realtime-6.8 < 6.8.1-1025.26~22.04.1
Fix: upgrade to 6.8.1-1025.26~22.04.1
Ubuntu:24.04:LTS canonical linux < 6.8.0-64.67
Fix: upgrade to 6.8.0-64.67
Ubuntu:24.04:LTS canonical linux-aws < 6.8.0-1032.34
Fix: upgrade to 6.8.0-1032.34
Ubuntu:24.04:LTS canonical linux-azure < 6.8.0-1034.39
Fix: upgrade to 6.8.0-1034.39
Ubuntu:24.04:LTS canonical linux-azure-6.11 < 6.11.0-1015.15~24.04.1
Fix: upgrade to 6.11.0-1015.15~24.04.1
Ubuntu:24.04:LTS canonical linux-azure-nvidia < 6.8.0-1022.23
Fix: upgrade to 6.8.0-1022.23
Ubuntu:24.04:LTS canonical linux-gcp < 6.8.0-1033.35
Fix: upgrade to 6.8.0-1033.35
Ubuntu:24.04:LTS canonical linux-gcp-6.11 < 6.11.0-1015.15~24.04.1
Fix: upgrade to 6.11.0-1015.15~24.04.1
Ubuntu:24.04:LTS canonical linux-gke < 6.8.0-1028.32
Fix: upgrade to 6.8.0-1028.32
Ubuntu:24.04:LTS canonical linux-gkeop < 6.8.0-1015.17
Fix: upgrade to 6.8.0-1015.17
Ubuntu:24.04:LTS canonical linux-hwe-6.11 < 6.11.0-26.26~24.04.1
Fix: upgrade to 6.11.0-26.26~24.04.1
Ubuntu:24.04:LTS canonical linux-ibm < 6.8.0-1029.29
Fix: upgrade to 6.8.0-1029.29
Ubuntu:24.04:LTS canonical linux-lowlatency < 6.8.0-64.67.1
Fix: upgrade to 6.8.0-64.67.1
Ubuntu:24.04:LTS canonical linux-lowlatency-hwe-6.11 < 6.11.0-1014.15~24.04.1
Fix: upgrade to 6.11.0-1014.15~24.04.1
Ubuntu:24.04:LTS canonical linux-nvidia < 6.8.0-1031.34
Fix: upgrade to 6.8.0-1031.34
Ubuntu:24.04:LTS canonical linux-nvidia-6.11 < 6.11.0-1010.10
Fix: upgrade to 6.11.0-1010.10
Ubuntu:24.04:LTS canonical linux-nvidia-lowlatency < 6.8.0-1031.34.1
Fix: upgrade to 6.8.0-1031.34.1
Ubuntu:24.04:LTS canonical linux-nvidia-tegra < 6.8.0-1008.8
Fix: upgrade to 6.8.0-1008.8
Ubuntu:24.04:LTS canonical linux-oem-6.11 < 6.11.0-1022.22
Fix: upgrade to 6.11.0-1022.22
Ubuntu:24.04:LTS canonical linux-oem-6.8 < 6.8.0-1031.31
Fix: upgrade to 6.8.0-1031.31
Ubuntu:24.04:LTS canonical linux-oracle < 6.8.0-1029.30
Fix: upgrade to 6.8.0-1029.30
Ubuntu:24.04:LTS canonical linux-raspi < 6.8.0-1031.35
Fix: upgrade to 6.8.0-1031.35
Ubuntu:24.04:LTS canonical linux-raspi-realtime All versions
Ubuntu:24.04:LTS canonical linux-xilinx < 6.8.0-1017.18
Fix: upgrade to 6.8.0-1017.18
Ubuntu:Pro:Realtime:24.04:LTS canonical linux-raspi-realtime < 6.8.0-2026.27
Fix: upgrade to 6.8.0-2026.27
Ubuntu:Pro:Realtime:24.04:LTS canonical linux-realtime < 6.8.1-1025.26
Fix: upgrade to 6.8.1-1025.26
Ubuntu:Pro:FIPS-updates:24.04:LTS canonical linux-fips < 6.8.0-78.78+fips1
Fix: upgrade to 6.8.0-78.78+fips1
Root:Ubuntu:24.04 – linux < 6.8.0-146.146.aikido.89
< 6.8.0-147.147.aikido.90
Fix: upgrade to 6.8.0-146.146.aikido.89
Root:Ubuntu:24.04 – rootio-linux < 6.8.0-146.146.aikido.89
< 6.8.0-147.147.aikido.90
Fix: upgrade to 6.8.0-146.146.aikido.89
Original advisory text
rxrpc, afs: Fix peer hash locking vs RCU callback
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): [<ffffffff8244360e>] _raw_spin_unlock_irqrestore+0x2e/0x50
hardirqs last disabled at (972401): [<ffffffff82443328>] _raw_spin_lock_irqsave+0x18/0x60
softirqs last enabled at (972300): [<ffffffff810ffbbe>] handle_softirqs+0x3ee/0x430
softirqs last disabled at (972313): [<ffffffff810ffc54>] __irq_exit_rcu+0x44/0x110

other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&rxnet->peer_hash_lock);
<Interrupt>
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:
<IRQ>
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
</IRQ>
References
Fix within
Internet-facing 60 days
Internal At next upgrade
  • Not known to be exploited
  • Needs hands-on effort to exploit
  • Gives an attacker partial control
Severity
7.5 High
Exploitation
<1% chance of attack within 30 days
Type
CWE-667Improper Locking
Timeline
Published27 Feb 2025
Updated4 Nov 2026
First seen7 Mar 2026
Sources
CVE-2025-21809 · NVD
CVE-2025-21809 · MITRE
ROOT-OS-UBUNTU-2404-CVE-2025-21809 · OSV
CVE-2025-21809 · OSV
UBUNTU-CVE-2025-21809 · OSV
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