INFO: rcu detected stall in igmp_ifc_timer_expire

Status: upstream: reported on 2026/10/26 07:58
Reported-by: syzbot+4aae0c498784ae81fca1@syzkaller.appspotmail.com
First crash: 12d, last: 12d
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in igmp_ifc_timer_expire net 1 syz, C 57 2610d 2869d 13/29 fixed on 2019/10/09 10:54
upstream INFO: rcu detected stall in igmp_ifc_timer_expire (2) kvm 1 1 1656d 1656d 0/29 auto-closed as invalid on 2022/06/25 04:57
upstream BUG: soft lockup in igmp_ifc_timer_expire (2) prio:normal net 1 1 45d 41d 0/29 moderation: reported on 2026/09/28 01:20
android-5-15 BUG: soft lockup in igmp_ifc_timer_expire 1 1 35d 35d 0/2 premoderation: reported on 2026/10/03 06:08

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-....: (1 GPs behind) idle=aa9/1/0x4000000000000000 softirq=12871/12872 fqs=5244 
	(t=10502 jiffies g=17149 q=2461)
NMI backtrace for cpu 0
CPU: 0 PID: 6964 Comm: syz.4.578 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_dump_cpu_stacks+0x22d/0x380 kernel/rcu/tree_stall.h:349
 print_cpu_stall+0x31f/0x5f0 kernel/rcu/tree_stall.h:633
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x6ec/0x1120 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:2021
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4b0/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x397/0x8b0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:seqcount_lockdep_reader_access+0x196/0x1d0 include/linux/seqlock.h:106
Code: 00 4d 85 e4 75 16 e8 29 08 10 00 eb 15 e8 22 08 10 00 e8 3d af 5f 08 4d 85 e4 74 ea e8 13 08 10 00 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 43 c7 44 3e 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc90000006ae0 EFLAGS: 00000246
RAX: ffffffff81691b4d RBX: 0000000000000000 RCX: ffff8880356b8000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000006b98 R08: ffffffff910461c7 R09: 1ffffffff2208c38
R10: dffffc0000000000 R11: fffffbfff2208c39 R12: 0000000000000200
R13: 000001fb63109b96 R14: 1ffff92000000d5c R15: dffffc0000000000
 ktime_get_with_offset+0x90/0x320 kernel/time/timekeeping.c:872
 ktime_get_real include/linux/timekeeping.h:79 [inline]
 __net_timestamp include/linux/skbuff.h:3982 [inline]
 netif_rx_internal+0x379/0x550 net/core/dev.c:4993
 netif_rx+0x94/0x380 net/core/dev.c:5045
 veth_forward_skb drivers/net/veth.c:297 [inline]
 veth_xmit+0x603/0xa50 drivers/net/veth.c:350
 __netdev_start_xmit include/linux/netdevice.h:5049 [inline]
 netdev_start_xmit include/linux/netdevice.h:5063 [inline]
 xmit_one net/core/dev.c:3663 [inline]
 dev_hard_start_xmit+0x297/0x7d0 net/core/dev.c:3679
 __dev_queue_xmit+0x195d/0x2e50 net/core/dev.c:4306
 br_dev_queue_push_xmit+0x696/0x850 net/bridge/br_forward.c:53
 NF_HOOK+0x2f9/0x380 include/linux/netfilter.h:302
 br_forward_finish+0x74/0x80 net/bridge/br_forward.c:66
 NF_HOOK+0x2f9/0x380 include/linux/netfilter.h:302
 __br_forward+0x433/0x610 net/bridge/br_forward.c:115
 deliver_clone net/bridge/br_forward.c:131 [inline]
 maybe_deliver+0xb5/0x150 net/bridge/br_forward.c:190
 br_flood+0x2fc/0x450 net/bridge/br_forward.c:232
 br_dev_xmit+0x10d3/0x1580 net/bridge/br_device.c:104
 __netdev_start_xmit include/linux/netdevice.h:5049 [inline]
 netdev_start_xmit include/linux/netdevice.h:5063 [inline]
 xmit_one net/core/dev.c:3663 [inline]
 dev_hard_start_xmit+0x297/0x7d0 net/core/dev.c:3679
 __dev_queue_xmit+0x195d/0x2e50 net/core/dev.c:4306
 neigh_hh_output include/net/neighbour.h:493 [inline]
 neigh_output include/net/neighbour.h:507 [inline]
 ip_finish_output2+0xc77/0x10e0 net/ipv4/ip_output.c:228
 NF_HOOK_COND include/linux/netfilter.h:291 [inline]
 ip_output+0x2ba/0x3e0 net/ipv4/ip_output.c:434
 igmpv3_send_cr net/ipv4/igmp.c:727 [inline]
 igmp_ifc_timer_expire+0xa97/0xbf0 net/ipv4/igmp.c:817
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:finish_lock_switch+0x12f/0x290 kernel/sched/core.c:4804
Code: 83 c7 18 be ff ff ff ff e8 6e 70 74 08 85 c0 74 46 4d 85 ff 75 62 0f 1f 44 00 00 48 89 df e8 08 e4 7d 08 e8 a3 f2 2a 00 fb 5b <41> 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 2f 0e fe ff 43 80 3c 2c
RSP: 0018:ffffc900034bf778 EFLAGS: 00000282
RAX: 743c259db7305900 RBX: ffff88801a1d0000 RCX: 743c259db7305900
RDX: dffffc0000000000 RSI: ffffffff8a2b2b60 RDI: ffffffff8a7a4bc0
RBP: 1ffff110171c7613 R08: ffff8880b8e3b30b R09: 1ffff110171c7661
R10: dffffc0000000000 R11: ffffed10171c7662 R12: 1ffff110171c75c1
R13: dffffc0000000000 R14: ffff8880b8e3ae08 R15: 0000000000000000
 finish_task_switch+0x12f/0x650 kernel/sched/core.c:4921
 context_switch kernel/sched/core.c:5052 [inline]
 __schedule+0x11cb/0x4350 kernel/sched/core.c:6395
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6571
 preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6596
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 try_to_wake_up+0x6cc/0x1020 kernel/sched/core.c:4171
 wake_up_process kernel/sched/core.c:4234 [inline]
 wake_up_q+0x78/0xc0 kernel/sched/core.c:953
 futex_wake+0x4a9/0x540 kernel/futex/core.c:1702
 do_futex+0xd83/0x12b0 kernel/futex/core.c:4023
 __do_sys_futex kernel/futex/core.c:4095 [inline]
 __se_sys_futex+0x389/0x420 kernel/futex/core.c:4076
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f43b0f8b559
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:00007f43af15e0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007f43b1212368 RCX: 00007f43b0f8b559
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f43b121236c
RBP: 00007f43b1212360 R08: 001e8da4b20da4ea R09: 0000000000000000
R10: 0000000000000035 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f43b12123f8 R14: 00007ffe10572610 R15: 00007ffe105726f8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/26 07:57 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in igmp_ifc_timer_expire
* Struck through repros no longer work on HEAD.