INFO: rcu detected stall in wg_packet_send_staged_packets

Status: upstream: reported on 2026/07/05 13:04
Reported-by: syzbot+b559979e4e112cd4a2f6@syzkaller.appspotmail.com
First crash: 56d, last: 56d

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-....: (9669 ticks this GP) idle=56b4/1/0x4000000000000000 softirq=46259/46260 fqs=28
rcu: 	         hardirqs   softirqs   csw/system
rcu: 	 number:   705660          0            0
rcu: 	cputime:    12570      23814           28   ==> 36420(ms)
rcu: 	(t=10504 jiffies g=57113 q=481 ncpus=2)
rcu: rcu_preempt kthread starved for 3426 jiffies! g57113 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:26952 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 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: 13286 Comm: syz.1.2232 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__sanitizer_cov_trace_switch+0x58/0xe0 kernel/kcov.c:349
Code: 48 8b 06 48 85 c0 0f 84 a4 00 00 00 41 57 41 56 41 54 53 48 8d 4c 09 01 48 8b 54 24 20 65 4c 8b 05 bd cd 7c 7e 45 31 c9 eb 08 <49> ff c1 4c 39 c8 74 77 4e 8b 54 ce 10 65 44 8b 1d ab cd 7c 7e 41
RSP: 0018:ffffc900001f0068 EFLAGS: 00000046
RAX: 0000000000000020 RBX: 0000000000000004 RCX: 0000000000000005
RDX: ffffffff8188b415 RSI: ffffffff8d17b080 RDI: 0000000000000004
RBP: 00000000000009ec R08: ffff888023a91e00 R09: 0000000000000019
R10: 0000000000000019 R11: 0000000000000100 R12: dffffc0000000000
R13: f800000000000000 R14: ffff88801ce4b0c4 R15: 00000000000b88a4
FS:  00007f7da82686c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f78f4558060 CR3: 000000007e45f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 rb_event_length+0x45/0x3f0 kernel/trace/ring_buffer.c:198
 check_buffer+0x542/0x950 kernel/trace/ring_buffer.c:3493
 __rb_reserve_next+0x4d9/0xd00 kernel/trace/ring_buffer.c:3626
 rb_reserve_next_event kernel/trace/ring_buffer.c:3761 [inline]
 ring_buffer_lock_reserve+0xae1/0xed0 kernel/trace/ring_buffer.c:3820
 __trace_buffer_lock_reserve kernel/trace/trace.c:996 [inline]
 trace_event_buffer_lock_reserve+0x1d2/0x6f0 kernel/trace/trace.c:2905
 trace_event_buffer_reserve+0x2ac/0x3d0 kernel/trace/trace_events.c:661
 do_trace_event_raw_event_bpf_trace_printk kernel/trace/bpf_trace.h:11 [inline]
 trace_event_raw_event_bpf_trace_printk+0x116/0x230 kernel/trace/bpf_trace.h:11
 trace_bpf_trace_printk+0x13e/0x1a0 kernel/trace/bpf_trace.h:11
 ____bpf_trace_printk kernel/trace/bpf_trace.c:388 [inline]
 bpf_trace_printk+0x142/0x1c0 kernel/trace/bpf_trace.c:371
 bpf_prog_b1bcf1c1da0a8648+0x40/0x44
 bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
 __bpf_prog_run include/linux/filter.h:616 [inline]
 bpf_prog_run include/linux/filter.h:623 [inline]
 bpf_prog_run_array include/linux/bpf.h:1994 [inline]
 trace_call_bpf+0x333/0x6c0 kernel/trace/bpf_trace.c:143
 perf_trace_run_bpf_submit+0x7a/0x1c0 kernel/events/core.c:10287
 perf_trace_preemptirq_template+0x269/0x330 include/trace/events/preemptirq.h:14
 trace_irq_enable+0xbb/0xe0 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x18/0x40 kernel/trace/trace_preemptirq.c:56
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:should_resched arch/x86/include/asm/preempt.h:104 [inline]
RIP: 0010:__local_bh_enable_ip+0x142/0x1c0 kernel/softirq.c:413
Code: 8a e8 32 92 39 09 65 66 8b 05 2a 6c b1 7e 66 85 c0 75 54 bf 01 00 00 00 e8 2b 1d 0a 00 e8 d6 06 3b 00 fb 65 8b 05 f6 6b b1 7e <85> c0 75 05 e8 a5 50 ae ff 48 c7 04 24 0e 36 e0 45 4b c7 04 37 00
RSP: 0018:ffffc900001f0940 EFLAGS: 00000286
RAX: 0000000000000101 RBX: 0000000000000201 RCX: acc957d058605c00
RDX: dffffc0000000000 RSI: ffffffff8acacb60 RDI: ffffffff8b1cfa20
RBP: ffffc900001f09d0 R08: ffffffff911e75ff R09: 1ffffffff223cebf
R10: dffffc0000000000 R11: fffffbfff223cec0 R12: ffffffff85b42acb
R13: ffffc900001f0ab0 R14: dffffc0000000000 R15: 1ffff9200003e128
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 wg_packet_send_staged_packets+0x151b/0x1850 drivers/net/wireguard/send.c:408
 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:finish_task_switch+0x267/0x8f0 kernel/sched/core.c:5255
Code: 2e 09 85 c0 0f 84 30 01 00 00 48 85 db 0f 85 4f 01 00 00 0f 1f 44 00 00 4c 89 e7 e8 43 32 38 09 e8 8e 0a 30 00 fb 4c 8b 65 b8 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0
RSP: 0018:ffffc9000bb5f960 EFLAGS: 00000286
RAX: acc957d058605c00 RBX: 0000000000000000 RCX: acc957d058605c00
RDX: dffffc0000000000 RSI: ffffffff8acacb60 RDI: ffffffff8b1cfa20
RBP: ffffc9000bb5f9b0 R08: ffffffff911e75ff R09: 1ffffffff223cebf
R10: dffffc0000000000 R11: fffffbfff223cec0 R12: ffff888023a91e00
R13: 1ffff110171e79a9 R14: dffffc0000000000 R15: ffff8880b8f3cd48
 context_switch kernel/sched/core.c:5384 [inline]
 __schedule+0x15b6/0x4660 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 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:__do_sys_perf_event_open kernel/events/core.c:12950 [inline]
RIP: 0010:__se_sys_perf_event_open+0x1841/0x1c60 kernel/events/core.c:12601
Code: 00 00 00 fc ff df 0f b6 04 08 84 c0 0f 85 03 03 00 00 48 8b 74 24 28 8b 96 fc 02 00 00 48 8b 5c 24 30 48 89 df e8 df 40 00 00 <48> 89 df e8 77 3b ff ff 48 8b 7c 24 50 e8 ed 70 e5 08 80 7c 24 1f
RSP: 0018:ffffc9000bb5fd40 EFLAGS: 00010246
RAX: acc957d058605c00 RBX: ffff88805d4c6000 RCX: 0000000000080000
RDX: ffffc9000cd2b000 RSI: 0000000000011824 RDI: 0000000000011825
RBP: ffffc9000bb5ff10 R08: ffffffff911e75ff R09: 1ffffffff223cebf
R10: dffffc0000000000 R11: fffffbfff223cec0 R12: 0000000000000000
R13: 1ffff9200176bfb8 R14: 1ffff11004a4b352 R15: ffff888023a91e00
 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: 0033:0x7f7da739de59
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:00007f7da8268028 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007f7da7625fa0 RCX: 00007f7da739de59
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000200000000680
RBP: 00007f7da7433e6f R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7da7626038 R14: 00007f7da7625fa0 R15: 00007ffe8ae449d8
 </TASK>
CPU: 0 PID: 13281 Comm: syz.2.2231 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:unwind_done arch/x86/include/asm/unwind.h:50 [inline]
RIP: 0010:__unwind_start+0x4a9/0x730 arch/x86/kernel/unwind_orc.c:757
Code: 31 ff 89 c6 e8 48 92 4b 00 85 ed 0f 84 59 01 00 00 e8 8b 8e 4b 00 e9 42 fc ff ff e8 81 8e 4b 00 80 3c 24 00 0f 84 4f 01 00 00 <49> 89 de 49 c1 ee 03 43 0f b6 04 3e 84 c0 0f 85 33 02 00 00 8b 2b
RSP: 0018:ffffc90000007448 EFLAGS: 00000202
RAX: ffffffff813b56ef RBX: ffffc900000074a8 RCX: ffff88802214da00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffc90000007500 R09: 0000000000000000
R10: ffffc900000074a8 R11: fffff52000000ea1 R12: ffffc90000007448
R13: ffffc900000074c8 R14: 1ffff92000000e9a R15: dffffc0000000000
FS:  00007f0183e716c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f010a438680 CR3: 0000000025ad6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000200000000300
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xf8/0x190 arch/x86/kernel/stacktrace.c:24
 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:4029
 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:schedule_debug kernel/sched/core.c:5938 [inline]
RIP: 0010:__schedule+0x16e/0x4660 kernel/sched/core.c:6591
Code: f7 4d 8b 36 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 f7 e8 29 91 4b f7 49 81 3e 9d 6e ac 57 <0f> 85 c6 16 00 00 45 85 e4 4c 8b 74 24 28 75 60 49 83 c6 18 4c 89
RSP: 0018:ffffc900050f7740 EFLAGS: 00000246
RAX: 1ffff92000a1e000 RBX: ffffffff8ca90a30 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffc900050f78e0
RBP: ffffc900050f7950 R08: ffffc900050f78df R09: 0000000000000000
R10: ffffc900050f78d0 R11: fffff52000a1ef1c R12: 0000000000000001
R13: ffff8880b8e00000 R14: ffffc900050f0000 R15: ffff8880b8e3cca0
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 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:sched_mm_cid_remote_clear_old kernel/sched/core.c:11938 [inline]
RIP: 0010:task_mm_cid_work+0x3e3/0x770 kernel/sched/core.c:11997
Code: 0d e8 31 42 11 00 85 c0 0f 84 03 01 00 00 49 8d 9e 7c 15 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 <84> c0 0f 85 9c 01 00 00 83 3b 00 74 34 49 81 c6 40 05 00 00 4c 89
RSP: 0018:ffffc900050f7ac0 EFLAGS: 00000a07
RAX: 0000000000000000 RBX: ffff888023a9337c RCX: dffffc0000000000
RDX: 0000000000000000 RSI: ffffffff8acadce0 RDI: ffffffff8b1cfa20
RBP: ffffc900050f7bb0 R08: dffffc0000000000 R09: 1ffffffff223cea0
R10: dffffc0000000000 R11: fffffbfff223cea1 R12: 0000000000000001
R13: ffffffff815e4afd R14: ffff888023a91e00 R15: ffffe8ffffd3d840
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 get_signal+0x11da/0x1390 kernel/signal.c:2679
 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: 0033:0x7f0182f9de59
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:00007f0183e710e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f0183226098 RCX: 00007f0182f9de59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f0183226098
RBP: 00007f0183226090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0183226128 R14: 00007ffedc029aa0 R15: 00007ffedc029b88
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/05 13:03 linux-6.6.y da47cbc25466 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in wg_packet_send_staged_packets
* Struck through repros no longer work on HEAD.