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INFO: task hung in cleanup_net (2)

Status: premoderation: reported on 2026/02/21 10:56
Reported-by: syzbot+3d42ca2ef3e41afad3ae@syzkaller.appspotmail.com
First crash: 5d20h, last: 5d20h
▶ ▼ Similar bugs (16)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in cleanup_net (2) net 1 2 2499d 2499d 0/29 closed as invalid on 2019/05/08 13:05
android-6-12 INFO: task hung in cleanup_net 1 3 122d 200d 0/1 auto-obsoleted due to no activity on 2026/01/25 16:18
android-44 INFO: task hung in cleanup_net 1 10 2453d 2495d 0/2 auto-closed as invalid on 2019/10/25 08:38
upstream INFO: task hung in cleanup_net net 1 1 3003d 2991d 3/29 fixed on 2018/01/03 02:35
linux-5.15 INFO: task hung in cleanup_net (2) origin:lts-only 1 syz error 1 42d 42d 0/3 upstream: reported syz repro on 2026/01/15 10:26
linux-4.19 INFO: task hung in cleanup_net 1 1 2118d 2118d 0/1 auto-closed as invalid on 2020/09/08 00:00
linux-4.14 INFO: task hung in cleanup_net 1 C inconclusive 23 1506d 2511d 0/1 upstream: reported C repro on 2019/04/13 10:16
upstream INFO: task hung in cleanup_net (7) net 1 121 178d 595d 0/29 auto-obsoleted due to no activity on 2025/11/10 21:07
upstream INFO: task hung in cleanup_net (3) net 1 1 2433d 2433d 0/29 auto-closed as invalid on 2019/10/25 14:21
linux-5.15 INFO: task hung in cleanup_net 1 1 560d 560d 0/3 auto-obsoleted due to no activity on 2024/11/23 07:55
android-49 INFO: task hung in cleanup_net 1 4 2503d 2510d 0/3 auto-closed as invalid on 2019/10/18 21:44
upstream INFO: task hung in cleanup_net (4) net 1 2 2017d 2022d 0/29 auto-closed as invalid on 2020/11/17 15:39
android-414 INFO: task hung in cleanup_net 1 C 45 2371d 2514d 0/1 public: reported C repro on 2019/04/11 00:00
android-49 INFO: task hung in cleanup_net (2) 1 1 2287d 2287d 0/3 auto-closed as invalid on 2020/03/23 02:35
upstream INFO: task hung in cleanup_net (6) net 1 1 971d 971d 0/29 auto-obsoleted due to no activity on 2023/09/30 00:07
upstream INFO: task hung in cleanup_net (5) net 1 3 1744d 1789d 0/29 auto-closed as invalid on 2021/09/03 11:33

Sample crash report:
INFO: task kworker/u8:0:12 blocked for more than 126 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:0    state:D stack:0     pid:12    tgid:12    ppid:2      flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5996 [inline]
 __schedule+0x134f/0x1ea0 kernel/sched/core.c:7843
 __schedule_loop kernel/sched/core.c:7924 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7939
 schedule_preempt_disabled+0x14/0x30 kernel/sched/core.c:7996
 __mutex_lock_common kernel/locking/mutex.c:707 [inline]
 __mutex_lock+0x960/0x1bb0 kernel/locking/mutex.c:803
 __mutex_lock_slowpath+0xe/0x20 kernel/locking/mutex.c:1134
 mutex_lock+0x113/0x1d0 kernel/locking/mutex.c:285
 rcu_barrier+0x4d/0x540 kernel/rcu/tree.c:4589
 cleanup_net+0x908/0xc90 net/core/net_namespace.c:653
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x7d4/0x1020 kernel/workqueue.c:3319
 worker_thread+0xc70/0x10b0 kernel/workqueue.c:3400
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
INFO: task kworker/1:5:548 blocked for more than 126 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:5     state:D stack:0     pid:548   tgid:548   ppid:2      flags:0x00004000
Workqueue: events fqdir_free_fn
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5996 [inline]
 __schedule+0x134f/0x1ea0 kernel/sched/core.c:7843
 __schedule_loop kernel/sched/core.c:7924 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7939
 schedule_timeout+0xc7/0x3b0 kernel/time/timer.c:2596
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common+0x369/0x650 kernel/sched/completion.c:127
 wait_for_completion+0x1c/0x40 kernel/sched/completion.c:148
 rcu_barrier+0x415/0x540 kernel/rcu/tree.c:4657
 fqdir_free_fn+0x36/0x150 net/ipv4/inet_fragment.c:167
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x7d4/0x1020 kernel/workqueue.c:3319
 worker_thread+0xc70/0x10b0 kernel/workqueue.c:3400
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 e74179280c147a83e3a201a5967fe5af4e04851c
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2ba/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x142/0x2c0 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:41
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:267 [inline]
 watchdog+0xdad/0xf00 kernel/hung_task.c:423
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 20 Comm: rcuop/0 Not tainted syzkaller #0 e74179280c147a83e3a201a5967fe5af4e04851c
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:queued_spin_trylock include/asm-generic/qspinlock.h:94 [inline]
RIP: 0010:do_raw_spin_trylock include/linux/spinlock.h:193 [inline]
RIP: 0010:__raw_spin_trylock include/linux/spinlock_api_smp.h:89 [inline]
RIP: 0010:_raw_spin_trylock+0x92/0x140 kernel/locking/spinlock.c:138
Code: 43 c6 44 3c 04 04 be 04 00 00 00 e8 98 df 3e fc 48 89 d8 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 91 00 00 00 8b 03 89 44 24 20 <85> c0 75 78 4c 8d 74 24 20 48 89 df be 04 00 00 00 e8 98 df 3e fc
RSP: 0018:ffffc9000022f860 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff8881f6f50d00 RCX: ffffffff85a099e8
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8881f6f50d00
RBP: ffffc9000022f8f0 R08: ffff8881f6f50d03 R09: 1ffff1103edea1a0
R10: dffffc0000000000 R11: ffffed103edea1a1 R12: 1ffff92000045f0c
R13: dffffc0000000000 R14: 1ffff1103edea17d R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fadfe016038 CR3: 000000010cba2000 CR4: 00000000003526b0
Call Trace:
 <IRQ>
 rcu_nocb_bypass_lock kernel/rcu/tree_nocb.h:96 [inline]
 rcu_nocb_flush_bypass kernel/rcu/tree_nocb.h:358 [inline]
 rcu_nocb_try_bypass kernel/rcu/tree_nocb.h:446 [inline]
 call_rcu_nocb+0x3ff/0xc80 kernel/rcu/tree_nocb.h:606
 __call_rcu_common+0x43b/0x720 kernel/rcu/tree.c:3117
 call_rcu_hurry+0xf/0x30 kernel/rcu/tree.c:3149
 dst_release+0x1a3/0x240 net/core/dst.c:177
 refdst_drop include/net/dst.h:263 [inline]
 skb_dst_drop include/net/dst.h:275 [inline]
 __dev_queue_xmit+0x8a3/0x3690 net/core/dev.c:4475
 dev_queue_xmit include/linux/netdevice.h:3141 [inline]
 neigh_hh_output include/net/neighbour.h:535 [inline]
 neigh_output include/net/neighbour.h:549 [inline]
 ip6_finish_output2+0x1175/0x19c0 net/ipv6/ip6_output.c:141
 __ip6_finish_output net/ipv6/ip6_output.c:215 [inline]
 ip6_finish_output+0x54e/0xb40 net/ipv6/ip6_output.c:226
 NF_HOOK_COND include/linux/netfilter.h:306 [inline]
 ip6_output+0x1fe/0x420 net/ipv6/ip6_output.c:247
 dst_output include/net/dst.h:459 [inline]
 NF_HOOK include/linux/netfilter.h:317 [inline]
 ndisc_send_skb+0x7ed/0xd60 net/ipv6/ndisc.c:513
 ndisc_send_na+0x8bf/0xb40 net/ipv6/ndisc.c:578
 ndisc_recv_ns+0x8fe/0x1300 net/ipv6/ndisc.c:962
 ndisc_rcv+0x41a/0x650 net/ipv6/ndisc.c:1864
 icmpv6_rcv+0xee1/0x1790 net/ipv6/icmp.c:991
 ip6_protocol_deliver_rcu+0xbc5/0x12f0 net/ipv6/ip6_input.c:436
 ip6_input_finish net/ipv6/ip6_input.c:481 [inline]
 NF_HOOK include/linux/netfilter.h:317 [inline]
 ip6_input+0x1cd/0x3a0 net/ipv6/ip6_input.c:490
 ip6_mc_input+0x35a/0x6c0 net/ipv6/ip6_input.c:584
 dst_input include/net/dst.h:469 [inline]
 ip6_rcv_finish+0x360/0x3e0 net/ipv6/ip6_input.c:79
 NF_HOOK include/linux/netfilter.h:317 [inline]
 ipv6_rcv+0xf1/0x240 net/ipv6/ip6_input.c:309
 __netif_receive_skb_one_core net/core/dev.c:5763 [inline]
 __netif_receive_skb net/core/dev.c:5876 [inline]
 process_backlog+0x44b/0xad0 net/core/dev.c:6212
 __napi_poll+0xd0/0x610 net/core/dev.c:6863
 napi_poll net/core/dev.c:6932 [inline]
 net_rx_action+0x5ea/0xd80 net/core/dev.c:7054
 handle_softirqs+0x1aa/0x630 kernel/softirq.c:621
 __do_softirq+0xf/0x16 kernel/softirq.c:659
 do_softirq+0xb8/0x110 kernel/softirq.c:503
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x74/0x80 kernel/softirq.c:430
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_do_batch+0x5d9/0xd40 kernel/rcu/tree.c:2594
 nocb_cb_wait kernel/rcu/tree_nocb.h:923 [inline]
 rcu_nocb_cb_kthread+0x524/0xb30 kernel/rcu/tree_nocb.h:957
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
net_ratelimit: 76052 callbacks suppressed
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:1e:aa:b2:cd:35:99, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:1c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:1e:aa:b2:cd:35:99, vlan:0)
net_ratelimit: 102088 callbacks suppressed
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:1c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:1e:aa:b2:cd:35:99, vlan:0)

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/21 10:55 android16-6.12 7712ca595283 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in cleanup_net
* Struck through repros no longer work on HEAD.