syzbot


INFO: task hung in cleanup_net

Status: premoderation: reported on 2025/08/10 17:36
Reported-by: syzbot+2b82682e505a98ec3619@syzkaller.appspotmail.com
First crash: 107d, last: 29d
Similar bugs (14)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in cleanup_net (2) net 1 2 2406d 2406d 0/29 closed as invalid on 2019/05/08 13:05
android-44 INFO: task hung in cleanup_net 1 10 2360d 2402d 0/2 auto-closed as invalid on 2019/10/25 08:38
upstream INFO: task hung in cleanup_net net 1 1 2910d 2898d 3/29 fixed on 2018/01/03 02:35
linux-4.19 INFO: task hung in cleanup_net 1 1 2025d 2025d 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 1413d 2418d 0/1 upstream: reported C repro on 2019/04/13 10:16
upstream INFO: task hung in cleanup_net (7) net 1 121 85d 502d 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 2340d 2340d 0/29 auto-closed as invalid on 2019/10/25 14:21
linux-5.15 INFO: task hung in cleanup_net 1 1 467d 467d 0/3 auto-obsoleted due to no activity on 2024/11/23 07:55
android-49 INFO: task hung in cleanup_net 1 4 2410d 2417d 0/3 auto-closed as invalid on 2019/10/18 21:44
upstream INFO: task hung in cleanup_net (4) net 1 2 1924d 1929d 0/29 auto-closed as invalid on 2020/11/17 15:39
android-414 INFO: task hung in cleanup_net 1 C 45 2278d 2421d 0/1 public: reported C repro on 2019/04/11 00:00
android-49 INFO: task hung in cleanup_net (2) 1 1 2194d 2194d 0/3 auto-closed as invalid on 2020/03/23 02:35
upstream INFO: task hung in cleanup_net (6) net 1 1 878d 878d 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 1651d 1696d 0/29 auto-closed as invalid on 2021/09/03 11:33

Sample crash report:
INFO: task kworker/u8:2:46 blocked for more than 123 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:2    state:D stack:0     pid:46    tgid:46    ppid:2      flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x1322/0x1df0 kernel/sched/core.c:7791
 __schedule_loop kernel/sched/core.c:7872 [inline]
 schedule+0xc6/0x240 kernel/sched/core.c:7887
 schedule_preempt_disabled+0x14/0x30 kernel/sched/core.c:7944
 __mutex_lock_common kernel/locking/mutex.c:707 [inline]
 __mutex_lock+0x81e/0x1b50 kernel/locking/mutex.c:803
 __mutex_lock_slowpath+0xe/0x20 kernel/locking/mutex.c:1134
 mutex_lock+0x102/0x1c0 kernel/locking/mutex.c:285
 rcu_barrier+0x4d/0x530 kernel/rcu/tree.c:4589
 cleanup_net+0x8f2/0xc70 net/core/net_namespace.c:653
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x7d2/0x1020 kernel/workqueue.c:3319
 worker_thread+0xc58/0x1250 kernel/workqueue.c:3400
 kthread+0x2ca/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/0:5:764 blocked for more than 124 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:5     state:D stack:0     pid:764   tgid:764   ppid:2      flags:0x00004000
Workqueue: events fqdir_free_fn
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x1322/0x1df0 kernel/sched/core.c:7791
 __schedule_loop kernel/sched/core.c:7872 [inline]
 schedule+0xc6/0x240 kernel/sched/core.c:7887
 schedule_timeout+0xb2/0x3a0 kernel/time/timer.c:2595
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common+0x359/0x630 kernel/sched/completion.c:127
 wait_for_completion+0x1c/0x40 kernel/sched/completion.c:148
 rcu_barrier+0x415/0x530 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+0x7d2/0x1020 kernel/workqueue.c:3319
 worker_thread+0xc58/0x1250 kernel/workqueue.c:3400
 kthread+0x2ca/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 syz.2.1417:4452 blocked for more than 124 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.1417      state:D stack:0     pid:4452  tgid:4452  ppid:292    flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x1322/0x1df0 kernel/sched/core.c:7791
 __schedule_loop kernel/sched/core.c:7872 [inline]
 schedule+0xc6/0x240 kernel/sched/core.c:7887
 schedule_preempt_disabled+0x14/0x30 kernel/sched/core.c:7944
 __mutex_lock_common kernel/locking/mutex.c:707 [inline]
 __mutex_lock+0x81e/0x1b50 kernel/locking/mutex.c:803
 __mutex_lock_slowpath+0xe/0x20 kernel/locking/mutex.c:1134
 mutex_lock+0x102/0x1c0 kernel/locking/mutex.c:285
 rcu_barrier+0x4d/0x530 kernel/rcu/tree.c:4589
 netdev_run_todo+0x10e/0xcb0 net/core/dev.c:10880
 rtnl_unlock+0x12/0x20 net/core/rtnetlink.c:152
 tun_detach drivers/net/tun.c:704 [inline]
 tun_chr_close+0xc5/0x150 drivers/net/tun.c:3517
 __fput+0x1fb/0xa00 fs/file_table.c:429
 ____fput+0x20/0x30 fs/file_table.c:457
 task_work_run+0x1e0/0x250 kernel/task_work.c:240
 resume_user_mode_work+0x36/0x50 include/linux/resume_user_mode.h:50
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x64/0xb0 kernel/entry/common.c:218
 do_syscall_64+0x64/0xf0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fe1f178efc9
RSP: 002b:00007fffe8bb7f68 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 0000000000018468 RCX: 00007fe1f178efc9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fe1f19e7da0 R08: 0000000000000001 R09: 00000018e8bb825f
R10: 0000001b2df20000 R11: 0000000000000246 R12: 00007fe1f19e5fac
R13: 00007fe1f19e5fa0 R14: ffffffffffffffff R15: 00007fffe8bb8080
 </TASK>
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 0b5ffdee5fcd2f7749818d1ff954e9c21353764e
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x10c/0x190 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2bf/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+0xd8f/0xed0 kernel/hung_task.c:423
 kthread+0x2ca/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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 4585 Comm: syz-executor Not tainted syzkaller #0 0b5ffdee5fcd2f7749818d1ff954e9c21353764e
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:update_stack_state+0x135/0x4b0 arch/x86/kernel/unwind_frame.c:-1
Code: ff ff ff 4c 89 f6 48 c1 ee 03 48 89 b5 40 ff ff ff 48 89 8d 70 ff ff ff 48 c1 e9 03 48 89 8d 48 ff ff ff 48 89 95 58 ff ff ff <48> c1 ea 03 48 89 95 68 ff ff ff 48 89 45 c0 48 c1 e8 03 48 89 45
RSP: 0018:ffffc900000070b8 EFLAGS: 00000a02
RAX: ffffc90000007230 RBX: ffffc90000007208 RCX: 1ffff92000000e43
RDX: ffffc90000007220 RSI: 1ffff92000000e42 RDI: ffffc90000007260
RBP: ffffc90000007178 R08: ffffc900000072d0 R09: ffffc900000072c8
R10: 0000000000000011 R11: ffffffff817457d0 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffc90000007210 R15: ffffc90011507510
FS:  0000000000000000(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005560a901eb98 CR3: 00000000072a8000 CR4: 00000000003526b0
Call Trace:
 <IRQ>
 unwind_next_frame+0x3c2/0x750 arch/x86/kernel/unwind_frame.c:315
 arch_stack_walk+0x139/0x170 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9d/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:69
 kasan_save_alloc_info+0x40/0x50 mm/kasan/generic.c:565
 unpoison_slab_object mm/kasan/common.c:320 [inline]
 __kasan_slab_alloc+0x73/0x90 mm/kasan/common.c:346
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4178 [inline]
 slab_alloc_node mm/slub.c:4227 [inline]
 kmem_cache_alloc_noprof+0x1cb/0x430 mm/slub.c:4236
 skb_clone+0x229/0x460 net/core/skbuff.c:2082
 deliver_clone net/bridge/br_forward.c:125 [inline]
 maybe_deliver net/bridge/br_forward.c:190 [inline]
 br_flood+0x4ed/0x730 net/bridge/br_forward.c:236
 br_handle_frame_finish+0x12bb/0x1720 net/bridge/br_input.c:215
 nf_hook_bridge_pre net/bridge/br_input.c:301 [inline]
 br_handle_frame+0x5a6/0xba0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xf4b/0x3940 net/core/dev.c:5663
 __netif_receive_skb_one_core net/core/dev.c:5767 [inline]
 __netif_receive_skb net/core/dev.c:5882 [inline]
 process_backlog+0x3e5/0xae0 net/core/dev.c:6218
 __napi_poll+0xd3/0x610 net/core/dev.c:6869
 napi_poll net/core/dev.c:6938 [inline]
 net_rx_action+0x584/0xce0 net/core/dev.c:7060
 handle_softirqs+0x1ab/0x630 kernel/softirq.c:621
 __do_softirq+0xf/0x16 kernel/softirq.c:659
 do_softirq+0xa6/0x100 kernel/softirq.c:503
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x74/0x80 kernel/softirq.c:430
 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:167 [inline]
 _raw_spin_unlock_bh+0x54/0x60 kernel/locking/spinlock.c:210
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 addrconf_ifdown+0x608/0x1940 net/ipv6/addrconf.c:3950
 addrconf_notify+0x17a/0xea0 net/ipv6/addrconf.c:-1
 notifier_call_chain+0x10b/0x2c0 kernel/notifier.c:93
 raw_notifier_call_chain+0x31/0x40 kernel/notifier.c:461
 call_netdevice_notifiers_info net/core/dev.c:2067 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2105 [inline]
 call_netdevice_notifiers net/core/dev.c:2119 [inline]
 unregister_netdevice_many_notify+0xe32/0x1bd0 net/core/dev.c:11501
 unregister_netdevice_many net/core/dev.c:11563 [inline]
 unregister_netdevice_queue+0x339/0x380 net/core/dev.c:11437
 unregister_netdevice include/linux/netdevice.h:3165 [inline]
 __tun_detach+0xca1/0x1460 drivers/net/tun.c:685
 tun_detach drivers/net/tun.c:701 [inline]
 tun_chr_close+0x93/0x150 drivers/net/tun.c:3517
 __fput+0x1fb/0xa00 fs/file_table.c:429
 ____fput+0x20/0x30 fs/file_table.c:457
 task_work_run+0x1e0/0x250 kernel/task_work.c:240
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x9bc/0x2630 kernel/exit.c:953
 do_group_exit+0x22a/0x300 kernel/exit.c:1095
 get_signal+0x139d/0x14f0 kernel/signal.c:2933
 arch_do_signal_or_restart+0x96/0x720 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x58/0xb0 kernel/entry/common.c:218
 do_syscall_64+0x64/0xf0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f3379590e03
Code: Unable to access opcode bytes at 0x7f3379590dd9.
RSP: 002b:00007ffe0a364df8 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: 0000000000000028 RBX: 00007f337a314620 RCX: 00007f3379590e03
RDX: 0000000000000028 RSI: 00007f337a314670 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007ffe0a364e14 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f337a314670 R15: 0000000000000000
 </TASK>
net_ratelimit: 111720 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:fe:72:e2:fe:ee:21, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
net_ratelimit: 132655 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/27 16:15 android16-6.12 0d6730ee6542 fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in cleanup_net
2025/09/05 16:33 android16-6.12 c5058bfb5bf2 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in cleanup_net
2025/08/10 17:35 android16-6.12 d0c633175c04 32a0e5ed .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.