INFO: rcu detected stall in neigh_timer_handler (2)

Status: upstream: reported on 2026/07/25 18:11
Reported-by: syzbot+c20fba0ef911a918a9d2@syzkaller.appspotmail.com
First crash: 2d05h, last: 2d05h
▶ ▼ Similar bugs (26)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in neigh_timer_handler (6) netfilter 1 1 2056d 2056d 0/29 auto-closed as invalid on 2021/03/09 03:20
linux-6.6 INFO: rcu detected stall in neigh_timer_handler 1 1 145d 145d 0/2 auto-obsoleted due to no activity on 2026/06/12 03:02
upstream INFO: rcu detected stall in neigh_timer_handler (8) net 1 C done done 72 715d 775d 28/29 fixed on 2024/10/21 12:45
upstream INFO: rcu detected stall in neigh_timer_handler net 1 1 2802d 2802d 0/29 auto-closed as invalid on 2019/05/23 06:47
upstream INFO: rcu detected stall in neigh_timer_handler (2) net 1 2 2512d 2513d 13/29 fixed on 2019/10/09 10:54
upstream INFO: rcu detected stall in neigh_timer_handler (4) net 1 1 2427d 2427d 0/29 closed as invalid on 2019/12/04 14:04
linux-5.15 INFO: rcu detected stall in neigh_timer_handler 1 1 316d 316d 0/3 auto-obsoleted due to no activity on 2025/12/23 11:36
upstream INFO: rcu detected stall in neigh_timer_handler (5) net 1 1 2159d 2159d 0/29 auto-closed as invalid on 2020/11/26 10:25
linux-5.15 INFO: rcu detected stall in neigh_timer_handler (2) 1 2 153d 155d 0/3 auto-obsoleted due to no activity on 2026/06/04 18:05
upstream INFO: rcu detected stall in neigh_timer_handler (3) net 1 2 2432d 2432d 0/29 closed as invalid on 2019/11/29 14:24
linux-6.1 INFO: rcu detected stall in neigh_timer_handler (3) 1 1 285d 285d 0/3 auto-obsoleted due to no activity on 2026/01/23 04:30
upstream INFO: rcu detected stall in neigh_timer_handler (7) net 1 1 1932d 1932d 0/29 auto-closed as invalid on 2021/07/11 19:14
linux-6.1 INFO: rcu detected stall in neigh_timer_handler (2) 1 1 539d 539d 0/3 auto-obsoleted due to no activity on 2025/05/14 07:23
linux-4.14 INFO: rcu detected stall in neigh_timer_handler 1 5 2277d 2396d 0/1 auto-closed as invalid on 2020/08/30 16:21
linux-6.1 INFO: rcu detected stall in neigh_timer_handler 1 4 670d 781d 0/3 auto-obsoleted due to no activity on 2025/01/03 05:12
upstream BUG: soft lockup in neigh_timer_handler (2) net 1 2 550d 580d 0/29 closed as invalid on 2025/02/28 15:46
upstream BUG: soft lockup in neigh_timer_handler (4) perf 1 1 121d 121d 0/29 closed as invalid on 2026/05/19 12:17
android-5-10 BUG: soft lockup in neigh_timer_handler 1 2 1068d 1076d 0/2 auto-obsoleted due to no activity on 2023/11/22 05:43
linux-4.19 BUG: soft lockup in neigh_timer_handler 1 4 1353d 1612d 0/1 auto-obsoleted due to no activity on 2023/03/12 06:57
android-54 BUG: soft lockup in neigh_timer_handler (2) 1 5 438d 523d 0/2 auto-obsoleted due to no activity on 2025/08/13 05:16
linux-4.14 BUG: soft lockup in neigh_timer_handler 1 3 1622d 1665d 0/1 auto-closed as invalid on 2022/06/16 21:59
android-5-15 BUG: soft lockup in neigh_timer_handler 1 1 17d 17d 0/2 premoderation: reported on 2026/07/10 13:24
upstream BUG: soft lockup in neigh_timer_handler (3) batman 1 2 450d 450d 0/29 auto-obsoleted due to no activity on 2025/08/01 18:42
android-6-1 BUG: soft lockup in neigh_timer_handler 1 2 982d 1004d 0/2 auto-obsoleted due to no activity on 2024/02/16 02:11
android-54 BUG: soft lockup in neigh_timer_handler 1 3 767d 779d 0/2 auto-obsoleted due to no activity on 2024/09/18 13:19
upstream BUG: soft lockup in neigh_timer_handler net 1 1 1101d 1075d 0/29 auto-obsoleted due to no activity on 2023/10/20 21:15

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (1 GPs behind) idle=decc/1/0x4000000000000000 softirq=70671/70672 fqs=3
rcu: 	(t=10500 jiffies g=93137 q=111 ncpus=2)
rcu: rcu_preempt kthread starved for 10492 jiffies! g93137 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:26920 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x30d/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 19024 Comm: syz.1.4839 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:207 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:147 [inline]
RIP: 0010:wrmsr arch/x86/include/asm/msr.h:254 [inline]
RIP: 0010:native_apic_msr_write+0x39/0x50 arch/x86/include/asm/apic.h:196
Code: 74 2a 83 ff 30 74 25 eb 10 81 ff d0 00 00 00 74 1b 81 ff e0 00 00 00 74 13 c1 ef 04 81 c7 00 08 00 00 89 f9 89 f0 31 d2 0f 30 <66> 90 c3 89 f6 31 d2 e9 2b 7f 2b 03 66 2e 0f 1f 84 00 00 00 00 00
RSP: 0018:ffffc900001f0838 EFLAGS: 00000046
RAX: 00000000000004b5 RBX: ffff8880b8f282c0 RCX: 0000000000000838
RDX: 0000000000000000 RSI: 00000000000004b5 RDI: 0000000000000838
RBP: 0000000000000000 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: dffffc0000000000
R13: 0000000010004824 R14: 00000000000004b5 R15: 0000000000000020
FS:  00007ff7ebed96c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100000002 CR3: 0000000062445000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 apic_write arch/x86/include/asm/apic.h:404 [inline]
 lapic_next_event+0x11/0x20 arch/x86/kernel/apic/apic.c:448
 clockevents_program_event+0x1c0/0x310 kernel/time/clockevents.c:334
 hrtimer_interrupt+0x565/0x980 kernel/time/hrtimer.c:1893
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x51/0xc0 arch/x86/kernel/apic/apic.c:1088
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:kasan_quarantine_put+0x88/0x220 mm/kasan/quarantine.c:243
Code: e8 fd e4 ad ff 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 0f 85 83 00 00 00 41 f7 c7 00 02 00 00 74 01 fb 31 c0 <48> 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f c3 48 8d 80 40 7b 03 00 45
RSP: 0018:ffffc900001f0a78 EFLAGS: 00000206
RAX: 6fae01c53507e401 RBX: ffff88806ab85140 RCX: 6fae01c53507e400
RDX: dffffc0000000000 RSI: ffffffff8acacbe0 RDI: ffffffff8b1d0660
RBP: ffff88806ab85140 R08: ffffffff911eb617 R09: 1ffffffff223d6c2
R10: dffffc0000000000 R11: fffffbfff223d6c3 R12: 0000000000000000
R13: ffffc900001f0b10 R14: 0000000000095f20 R15: 0000000000000282
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 kmem_cache_free+0xf8/0x290 mm/slub.c:3852
 neigh_probe net/core/neighbour.c:1082 [inline]
 neigh_timer_handler+0xace/0xff0 net/core/neighbour.c:1162
 call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x570/0x810 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x27d/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:preempt_schedule_irq+0xba/0x150 kernel/sched/core.c:7011
Code: 00 00 43 c6 44 37 04 f8 74 0b 0f 0b 48 f7 03 08 00 00 00 74 6f bf 01 00 00 00 e8 e1 c2 c7 f6 e8 2c bd f8 f6 fb bf 01 00 00 00 <e8> 31 b4 ff ff 43 c6 44 37 08 00 48 c7 44 24 40 00 00 00 00 9c 8f
RSP: 0018:ffffc9000ca4f940 EFLAGS: 00000286
RAX: 6fae01c53507e400 RBX: 0000000000000000 RCX: 6fae01c53507e400
RDX: dffffc0000000000 RSI: ffffffff8acacbe0 RDI: 0000000000000001
RBP: ffffc9000ca4f9e0 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 1ffff92001949f28
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:kcov_task_exit+0xa/0x140 kernel/kcov.c:448
Code: 7c 7e 48 8b 80 10 16 00 00 48 89 87 10 16 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 66 0f 1f 00 41 57 41 56 41 54 <53> 48 8b 9f 08 16 00 00 48 85 db 0f 84 c5 00 00 00 49 89 fc 4c 8d
RSP: 0018:ffffc9000ca4faa0 EFLAGS: 00000293
RAX: ffffffff8152206e RBX: 0000000000000002 RCX: ffff888029945a00
RDX: 0000000000000000 RSI: ffffffff8acacbe0 RDI: ffff888029945a00
RBP: ffffc9000ca4fc30 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: ffff88802be8de8c
R13: ffff88802be8de80 R14: 1ffff11005328c63 R15: dffffc0000000000
 do_exit+0x292/0x2530 kernel/exit.c:823
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1026
 get_signal+0x12a6/0x1390 kernel/signal.c:2903
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff7eaf9de99
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff7ebed90e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffff5 RBX: 00007ff7eb226188 RCX: 00007ff7eaf9de99
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007ff7eb226188
RBP: 00007ff7eb226180 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff7eb226218 R14: 00007ffff70a3600 R15: 00007ffff70a36e8
 </TASK>
CPU: 0 PID: 19023 Comm: syz.1.4839 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__kernel_text_address+0x14/0x30 kernel/extable.c:79
Code: 40 4c 8c 8e e8 ed 06 86 00 eb b8 66 2e 0f 1f 84 00 00 00 00 00 90 66 0f 1f 00 53 48 89 fb e8 23 00 00 00 48 81 fb 00 b0 df 8f <0f> 93 c1 48 81 fb ab 71 f6 8f 0f 92 c2 20 ca 08 c2 0f b6 c2 5b c3
RSP: 0018:ffffc90000007470 EFLAGS: 00000207
RAX: 0000000000000000 RBX: 00007ff7eaf9de99 RCX: 7895e290bedf7000
RDX: 0000000000000003 RSI: ffffffff8acadd60 RDI: ffffffff8b1d0660
RBP: 0000000000000001 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: ffffffff8aa000d0
R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffff92000000e9e
FS:  00007ff7ebefa6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100000001 CR3: 0000000062445000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000200000000300
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 unwind_get_return_address+0x5d/0xc0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:600 [inline]
 dst_cow_metrics_generic+0x56/0x1b0 net/core/dst.c:196
 dst_metrics_write_ptr include/net/dst.h:133 [inline]
 dst_metric_set include/net/dst.h:194 [inline]
 icmp6_dst_alloc+0x237/0x400 net/ipv6/route.c:3333
 ndisc_send_skb+0x422/0x1480 net/ipv6/ndisc.c:493
 addrconf_rs_timer+0x36b/0x640 net/ipv6/addrconf.c:4036
 call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x570/0x810 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x27d/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5758
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc9000c867680 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 7895e290bedf7000
RDX: 0000000000000000 RSI: ffffffff8acadd60 RDI: ffffffff8b1d0660
RBP: ffffc9000c867798 R08: dffffc0000000000 R09: 1ffffffff223d6a2
R10: dffffc0000000000 R11: fffffbfff223d6a3 R12: 1ffff9200190cedc
R13: ffffffff8d216e80 R14: 0000000000000246 R15: dffffc0000000000
 __fs_reclaim_acquire mm/page_alloc.c:3600 [inline]
 fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:3614
 might_alloc include/linux/sched/mm.h:303 [inline]
 slab_pre_alloc_hook+0x2a/0x300 mm/slab.h:714
 slab_alloc_node mm/slub.c:3477 [inline]
 __kmem_cache_alloc_node+0x53/0x250 mm/slub.c:3534
 kmalloc_node_trace+0x26/0xe0 mm/slab_common.c:1111
 kmalloc_node include/linux/slab.h:616 [inline]
 kzalloc_node include/linux/slab.h:732 [inline]
 __get_vm_area_node+0x125/0x370 mm/vmalloc.c:2613
 __vmalloc_node_range+0x36f/0x1320 mm/vmalloc.c:3299
 __vmalloc_node mm/vmalloc.c:3404 [inline]
 __vmalloc+0x7a/0x90 mm/vmalloc.c:3418
 bpf_prog_alloc_no_stats+0x46/0x430 kernel/bpf/core.c:99
 bpf_prog_alloc+0x3d/0x1a0 kernel/bpf/core.c:137
 bpf_prog_load+0x6b2/0x1610 kernel/bpf/syscall.c:2684
 __sys_bpf+0x5ba/0x890 kernel/bpf/syscall.c:5478
 __do_sys_bpf kernel/bpf/syscall.c:5582 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5580 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5580
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff7eaf9de99
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff7ebefa028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007ff7eb226090 RCX: 00007ff7eaf9de99
RDX: 0000000000000048 RSI: 0000200000000200 RDI: 0000000000000005
RBP: 00007ff7eb033eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff7eb226128 R14: 00007ff7eb226090 R15: 00007ffff70a36e8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/25 18:11 linux-6.6.y c5596480c50e 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in neigh_timer_handler
* Struck through repros no longer work on HEAD.