syzbot


INFO: task hung in synchronize_rcu

Status: internal: reported on 2025/07/11 21:20
Reported-by: syzbot+0232e02d8636b4ed7022@syzkaller.appspotmail.com
First crash: 22d, last: 11h31m
Similar bugs (13)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in synchronize_rcu (3) 1 C done done 374 882d 1819d 22/29 fixed on 2023/02/24 13:50
linux-6.1 INFO: task hung in synchronize_rcu origin:lts-only 1 C unreliable 18 44d 837d 0/3 upstream: reported C repro on 2023/04/01 04:49
android-49 INFO: task hung in synchronize_rcu 1 1 2055d 2055d 0/3 auto-closed as invalid on 2020/03/28 16:57
linux-4.14 INFO: task hung in synchronize_rcu vfs 1 C error 162 896d 2078d 0/1 upstream: reported C repro on 2019/11/07 04:32
linux-4.19 INFO: task hung in synchronize_rcu 1 C error 70 885d 2076d 0/1 upstream: reported C repro on 2019/11/08 21:27
linux-5.15 INFO: task hung in synchronize_rcu 1 1 822d 822d 0/3 auto-obsoleted due to no activity on 2023/08/14 02:05
linux-5.15 INFO: task hung in synchronize_rcu (3) origin:lts-only 1 C error 14 1d23h 355d 0/3 upstream: reported C repro on 2024/07/26 03:55
upstream INFO: task hung in synchronize_rcu 1 syz done 1206 2055d 2081d 14/29 fixed on 2019/11/29 15:48
upstream INFO: task hung in synchronize_rcu (4) net fs 1 C done error 894 16d 804d 0/29 upstream: reported C repro on 2023/05/04 02:01
linux-5.15 INFO: task hung in synchronize_rcu (2) 1 1 510d 510d 0/3 auto-obsoleted due to no activity on 2024/05/31 13:53
android-414 INFO: task hung in synchronize_rcu 1 1 2073d 2073d 0/1 auto-closed as invalid on 2020/03/10 10:42
upstream INFO: task hung in synchronize_rcu (2) trace 1 8 2054d 2055d 0/29 closed as invalid on 2019/11/30 16:54
upstream INFO: task hung in rtnetlink_rcv_msg net 1 C inconclusive inconclusive 1970 372d 2335d 26/29 fixed on 2024/07/09 19:14

Sample crash report:
INFO: task syz.8.6850:20252 blocked for more than 123 seconds.
      Not tainted 6.12.30-syzkaller-g603af016e4a8 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.8.6850      state:D stack:0     pid:20252 tgid:20252 ppid:19082  flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x132b/0x1e00 kernel/sched/core.c:7789
 __schedule_loop kernel/sched/core.c:7870 [inline]
 schedule+0xc6/0x240 kernel/sched/core.c:7885
 schedule_preempt_disabled+0x14/0x30 kernel/sched/core.c:7942
 __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
 exp_funnel_lock kernel/rcu/tree_exp.h:329 [inline]
 synchronize_rcu_expedited+0x288/0x7b0 kernel/rcu/tree_exp.h:976
 namespace_unlock+0x1ec/0x3d0 fs/namespace.c:1704
 drop_collected_mounts fs/namespace.c:2232 [inline]
 put_mnt_ns+0xad/0xf0 fs/namespace.c:5578
 free_nsproxy+0x52/0x290 kernel/nsproxy.c:193
 put_nsproxy include/linux/nsproxy.h:118 [inline]
 switch_task_namespaces kernel/nsproxy.c:251 [inline]
 exit_task_namespaces+0x99/0xe0 kernel/nsproxy.c:256
 do_exit+0x9af/0x2630 kernel/exit.c:943
 do_group_exit+0x22a/0x300 kernel/exit.c:1094
 get_signal+0x139d/0x14f0 kernel/signal.c:2934
 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: 0033:0x7f6454dc11e5
RSP: 002b:00007f6455ba7f80 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: fffffffffffffdfc RBX: 00007f6454fb5fa0 RCX: 00007f6454dc11e5
RDX: 00007f6455ba7fc0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f6454e10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f6454fb5fa0 R15: 00007ffe92899bf8
 </TASK>
INFO: task syz.8.7672:22625 blocked for more than 125 seconds.
      Not tainted 6.12.30-syzkaller-g603af016e4a8 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.8.7672      state:D stack:0     pid:22625 tgid:22619 ppid:19082  flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x132b/0x1e00 kernel/sched/core.c:7789
 __schedule_loop kernel/sched/core.c:7870 [inline]
 schedule+0xc6/0x240 kernel/sched/core.c:7885
 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_state+0x19/0x40 kernel/sched/completion.c:264
 __wait_rcu_gp+0x296/0x2c0 kernel/rcu/update.c:514
 synchronize_rcu_normal+0x113/0x160 kernel/rcu/tree.c:4031
 synchronize_rcu+0x98/0x2e0 kernel/rcu/tree.c:4109
 synchronize_net+0x38/0x40 net/core/dev.c:11366
 packet_release+0x9f8/0xd50 net/packet/af_packet.c:3217
 __sock_release net/socket.c:659 [inline]
 sock_close+0xdd/0x280 net/socket.c:1427
 __fput+0x1fb/0xa00 fs/file_table.c:431
 ____fput+0x20/0x30 fs/file_table.c:459
 task_work_run+0x1e3/0x250 kernel/task_work.c:240
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x9b4/0x2630 kernel/exit.c:944
 do_group_exit+0x22a/0x300 kernel/exit.c:1094
 get_signal+0x139d/0x14f0 kernel/signal.c:2934
 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: 0033:0x7f6454d8e929
RSP: 002b:00007f6455ba8038 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
RAX: 0000000000000008 RBX: 00007f6454fb5fa0 RCX: 00007f6454d8e929
RDX: 0000000000000300 RSI: 0000000000000003 RDI: 0000000000000011
RBP: 00007f6454e10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f6454fb5fa0 R15: 00007ffe92899bf8
 </TASK>
INFO: task syz.5.7673:22621 blocked for more than 127 seconds.
      Not tainted 6.12.30-syzkaller-g603af016e4a8 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.7673      state:D stack:0     pid:22621 tgid:22621 ppid:19821  flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x132b/0x1e00 kernel/sched/core.c:7789
 __schedule_loop kernel/sched/core.c:7870 [inline]
 schedule+0xc6/0x240 kernel/sched/core.c:7885
 synchronize_rcu_expedited+0x6b0/0x7b0 kernel/rcu/tree_exp.h:991
 namespace_unlock+0x1ec/0x3d0 fs/namespace.c:1704
 drop_collected_mounts fs/namespace.c:2232 [inline]
 put_mnt_ns+0xad/0xf0 fs/namespace.c:5578
 free_nsproxy+0x52/0x290 kernel/nsproxy.c:193
 put_nsproxy include/linux/nsproxy.h:118 [inline]
 switch_task_namespaces kernel/nsproxy.c:251 [inline]
 exit_task_namespaces+0x99/0xe0 kernel/nsproxy.c:256
 do_exit+0x9af/0x2630 kernel/exit.c:943
 do_group_exit+0x22a/0x300 kernel/exit.c:1094
 get_signal+0x139d/0x14f0 kernel/signal.c:2934
 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: 0033:0x7f8a69d8e929
RSP: 002b:00007ffdd6b66aa8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f8a69fb7ba0 RCX: 00007f8a69d8e929
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f8a69fb7ba0 R08: 0000000000000170 R09: 00000013d6b66d9f
R10: 00007f8a69fb7ac0 R11: 0000000000000246 R12: 00000000000943a2
R13: 00007ffdd6b66ba0 R14: ffffffffffffffff R15: 00007ffdd6b66bc0
 </TASK>
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted 6.12.30-syzkaller-g603af016e4a8 #0 c515e79d845c5a778cd5838f9063bc4edcb1333e
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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+0x2c7/0x370 kernel/kthread.c:389
 ret_from_fork+0x64/0xa0 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: 11558 Comm: kworker/1:5 Not tainted 6.12.30-syzkaller-g603af016e4a8 #0 c515e79d845c5a778cd5838f9063bc4edcb1333e
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: mld mld_query_work
RIP: 0010:deliver_ptype_list_skb net/core/dev.c:2328 [inline]
RIP: 0010:__netif_receive_skb_core+0x2db7/0x3940 net/core/dev.c:5708
Code: 7f bd 1a fd e9 3d fe ff ff e8 75 bd 1a fd eb 1a e8 6e bd 1a fd 41 bc 01 00 00 00 e9 25 06 00 00 e8 5e bd 1a fd 4c 8b 74 24 08 <4c> 89 b4 24 f0 00 00 00 48 8b 44 24 40 48 8b 8c 24 00 02 00 00 48
RSP: 0018:ffffc90000230960 EFLAGS: 00000246
RAX: ffffffff846aed8b RBX: ffffffff87cad4e0 RCX: ffff88812da51300
RDX: 0000000000000100 RSI: 000000000000dd86 RDI: 000000000000dd86
RBP: ffffc90000230be8 R08: ffff88812da51300 R09: 0000000000000002
R10: 000000000000a888 R11: 0000000000000100 R12: 0000000000000001
R13: dffffc0000000000 R14: ffffffff87cb6f08 R15: ffffffff87cad4e0
FS:  0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff7538cfec CR3: 00000000072a8000 CR4: 00000000003526b0
Call Trace:
 <IRQ>
 __netif_receive_skb_one_core net/core/dev.c:5755 [inline]
 __netif_receive_skb net/core/dev.c:5870 [inline]
 process_backlog+0x3e5/0xae0 net/core/dev.c:6202
 __napi_poll+0xd0/0x610 net/core/dev.c:6853
 napi_poll net/core/dev.c:6922 [inline]
 net_rx_action+0x584/0xce0 net/core/dev.c:7044
 handle_softirqs+0x1ae/0x630 kernel/softirq.c:603
 __do_softirq+0xf/0x16 kernel/softirq.c:641
 do_softirq+0xa6/0x100 kernel/softirq.c:485
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x74/0x80 kernel/softirq.c:412
 __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]
 mld_query_work+0x951/0x2c10 net/ipv6/mcast.c:1529
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x7d5/0x1020 kernel/workqueue.c:3319
 worker_thread+0xc58/0x1250 kernel/workqueue.c:3400
 kthread+0x2c7/0x370 kernel/kthread.c:389
 ret_from_fork+0x64/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
net_ratelimit: 117534 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:de:15:4f:89:47:d6, 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 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)

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/15 19:24 android16-6.12 603af016e4a8 03fcfc4b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/12 20:23 android16-6.12 21ed84930c16 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/12 13:03 android16-6.12 21ed84930c16 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/11 00:05 android16-6.12 8ea40f524391 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/10 10:32 android16-6.12 d893caf112c8 956bd956 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/08 17:41 android16-6.12 15d2fe054444 4d9fdfa4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/08 10:31 android16-6.12 f6ca783ba264 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/07 00:11 android16-6.12 e2bf362ee23b 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/04 17:24 android16-6.12 e2bf362ee23b d869b261 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/03 23:49 android16-6.12 e2bf362ee23b 76ad128c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/07/02 06:25 android16-6.12 c40c54e66959 bc80e4f0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
2025/06/24 05:10 android16-6.12 1d4f4d446dbd e2f27c35 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in synchronize_rcu
* Struck through repros no longer work on HEAD.