syzbot


INFO: task hung in io_wq_put_and_exit

Status: upstream: reported C repro on 2025/06/25 22:50
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+ea8018030af6aec75b1e@syzkaller.appspotmail.com
First crash: 305d, last: 14d
Fix commit to backport (bisect log) :
tree: upstream
commit bcb0fda3c2da9fe4721d3e73d80e778c038e7d27
Author: Jens Axboe <axboe@kernel.dk>
Date: Wed Mar 5 21:03:34 2025 +0000

  io_uring/rw: ensure reissue path is correctly handled for IOPOLL

  
Bug presence (2)
Date Name Commit Repro Result
2025/12/31 linux-6.6.y (ToT) 5fa4793a2d2d C [report] INFO: task hung in io_wq_put_and_exit
2025/12/31 upstream (ToT) dbf8fe85a16a C Didn't crash
Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in io_wq_put_and_exit (6) io-uring 1 C error 74 93d 252d 28/29 upstream: reported C repro on 2025/08/18 08:05
linux-5.15 INFO: task hung in io_wq_put_and_exit 1 1 777d 777d 0/3 auto-obsoleted due to no activity on 2024/06/19 08:55
upstream INFO: task hung in io_wq_put_and_exit (3) io-uring 1 C error unreliable 75 1101d 1495d 0/29 auto-obsoleted due to no activity on 2023/08/20 08:26
upstream INFO: task hung in io_wq_put_and_exit io-uring fs 1 C unreliable 628 1630d 1691d 20/29 fixed on 2021/11/10 00:50
upstream INFO: task hung in io_wq_put_and_exit (2) fs 1 22 1599d 1628d 0/29 closed as invalid on 2022/02/08 09:40
upstream INFO: task hung in io_wq_put_and_exit (5) io-uring input usb 1 C done 9 258d 277d 0/29 closed as invalid on 2025/08/13 14:32
upstream INFO: task hung in io_wq_put_and_exit (4) io-uring 1 C unreliable 86 325d 554d 28/29 fixed on 2025/06/10 16:19
Last patch testing requests (2)
Created Duration User Patch Repo Result
2025/08/11 15:38 51m sumanth.gavini@yahoo.com patch linux-6.6.y report log
2025/08/10 21:45 23m sumanth.gavini@yahoo.com patch linux-6.6.y report log
Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/08/07 00:08 9h48m fix candidate upstream OK (1) job log

Sample crash report:
INFO: task syz.1.18:5980 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.18        state:D stack:24656 pid:5980  ppid:5900   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion+0x2cb/0x5b0 kernel/sched/completion.c:148
 io_wq_exit_workers io_uring/io-wq.c:1266 [inline]
 io_wq_put_and_exit+0x474/0x810 io_uring/io-wq.c:1294
 io_uring_clean_tctx+0x130/0x1b0 io_uring/tctx.c:204
 io_uring_cancel_generic+0x610/0x6c0 io_uring/io_uring.c:3507
 io_uring_files_cancel include/linux/io_uring.h:69 [inline]
 do_exit+0x5f1/0x2460 kernel/exit.c:829
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 __do_sys_exit_group kernel/exit.c:1035 [inline]
 __se_sys_exit_group kernel/exit.c:1033 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1033
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f065199c799
RSP: 002b:00007ffe94be71b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f065199c799
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000000000000 R09: 00007f0651be63e0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0651be63e0 R14: 0000000000000003 R15: 00007ffe94be7270
 </TASK>
INFO: task syz.3.20:5982 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.20        state:D stack:25448 pid:5982  ppid:5905   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion+0x2cb/0x5b0 kernel/sched/completion.c:148
 io_wq_exit_workers io_uring/io-wq.c:1266 [inline]
 io_wq_put_and_exit+0x474/0x810 io_uring/io-wq.c:1294
 io_uring_clean_tctx+0x130/0x1b0 io_uring/tctx.c:204
 io_uring_cancel_generic+0x610/0x6c0 io_uring/io_uring.c:3507
 io_uring_files_cancel include/linux/io_uring.h:69 [inline]
 do_exit+0x5f1/0x2460 kernel/exit.c:829
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 __do_sys_exit_group kernel/exit.c:1035 [inline]
 __se_sys_exit_group kernel/exit.c:1033 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1033
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f5d1979c799
RSP: 002b:00007fff2d0e1a38 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f5d1979c799
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000000000000 R09: 00007f5d199e63e0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5d199e63e0 R14: 0000000000000003 R15: 00007fff2d0e1af0
 </TASK>
INFO: task syz.2.19:5987 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.19        state:D stack:25448 pid:5987  ppid:5902   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion+0x2cb/0x5b0 kernel/sched/completion.c:148
 io_wq_exit_workers io_uring/io-wq.c:1266 [inline]
 io_wq_put_and_exit+0x474/0x810 io_uring/io-wq.c:1294
 io_uring_clean_tctx+0x130/0x1b0 io_uring/tctx.c:204
 io_uring_cancel_generic+0x610/0x6c0 io_uring/io_uring.c:3507
 io_uring_files_cancel include/linux/io_uring.h:69 [inline]
 do_exit+0x5f1/0x2460 kernel/exit.c:829
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 __do_sys_exit_group kernel/exit.c:1035 [inline]
 __se_sys_exit_group kernel/exit.c:1033 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1033
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f513c39c799
RSP: 002b:00007ffe5f3a2d68 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f513c39c799
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000000000000 R09: 00007f513c5e63e0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f513c5e63e0 R14: 0000000000000003 R15: 00007ffe5f3a2e20
 </TASK>
INFO: task syz.0.17:5991 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:24712 pid:5991  ppid:5897   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion+0x2cb/0x5b0 kernel/sched/completion.c:148
 io_wq_exit_workers io_uring/io-wq.c:1266 [inline]
 io_wq_put_and_exit+0x474/0x810 io_uring/io-wq.c:1294
 io_uring_clean_tctx+0x130/0x1b0 io_uring/tctx.c:204
 io_uring_cancel_generic+0x610/0x6c0 io_uring/io_uring.c:3507
 io_uring_files_cancel include/linux/io_uring.h:69 [inline]
 do_exit+0x5f1/0x2460 kernel/exit.c:829
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 __do_sys_exit_group kernel/exit.c:1035 [inline]
 __se_sys_exit_group kernel/exit.c:1033 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1033
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f296ff9c799
RSP: 002b:00007ffda016cf28 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f296ff9c799
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000000000000 R09: 00007f29701e63e0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f29701e63e0 R14: 0000000000000003 R15: 00007ffda016cfe0
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8d132060 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8d132060 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8d132060 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by kworker/u4:4/55:
2 locks held by dhcpcd/5432:
 #0: ffff8880216a9690 (nlk_cb_mutex-ROUTE){+.+.}-{3:3}, at: __netlink_dump_start+0xf4/0x810 net/netlink/af_netlink.c:2336
 #1: ffffffff8e3c0d48 (rtnl_mutex){+.+.}-{3:3}, at: netlink_dump+0x78f/0xe50 net/netlink/af_netlink.c:2263
2 locks held by getty/5528:
 #0: ffff88802d8ea0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000326e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x433/0x1390 drivers/tty/n_tty.c:2217
1 lock held by syz-executor/6455:
1 lock held by syz-executor/6457:
 #0: ffffffff8e3c0d48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8e3c0d48 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x811/0xfa0 net/core/rtnetlink.c:6469
2 locks held by syz-executor/6472:
 #0: ffffffff8e3b3d10 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x351/0x5e0 net/core/net_namespace.c:516
 #1: ffffffff8e3c0d48 (rtnl_mutex){+.+.}-{3:3}, at: ip_tunnel_init_net+0x2cf/0x790 net/ipv4/ip_tunnel.c:1103
2 locks held by syz-executor/6475:
 #0: ffffffff8e3b3d10 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x351/0x5e0 net/core/net_namespace.c:516
 #1: ffffffff8e3c0d48 (rtnl_mutex){+.+.}-{3:3}, at: register_nexthop_notifier+0x88/0x240 net/ipv4/nexthop.c:3636

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf3d/0xf80 kernel/hung_task.c:379
 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>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 132 Comm: kworker/u4:5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:kasan_mem_to_shadow include/linux/kasan.h:60 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:127 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:178 [inline]
RIP: 0010:kasan_check_range+0x41/0x290 mm/kasan/generic.c:187
Code: 54 53 4c 8d 04 37 49 39 f8 0f 82 13 02 00 00 49 89 f9 49 c1 e9 2f 41 81 f9 ff ff 01 00 0f 82 ff 01 00 00 49 89 ff 49 c1 ef 03 <49> ba 00 00 00 00 00 fc ff df 4f 8d 1c 17 49 ff c8 4d 89 c1 49 c1
RSP: 0018:ffffc90002db7928 EFLAGS: 00000a02
RAX: ffffffff84aae401 RBX: 0000000000000040 RCX: ffffffff84aae558
RDX: 0000000000000001 RSI: 0000000000000040 RDI: ffffc90002db79a0
RBP: 0000000000000000 R08: ffffc90002db79e0 R09: 000000000001ffff
R10: dffffc0000000000 R11: fffffbfff22382bf R12: 1ffff920005b6f30
R13: 0000000000000002 R14: ffffc90002db79a0 R15: 1ffff920005b6f34
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f72dffe7420 CR3: 000000004b186000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 __asan_memset+0x22/0x40 mm/kasan/shadow.c:84
 memzero_explicit include/linux/string.h:279 [inline]
 _get_random_bytes+0x1e8/0x250 drivers/char/random.c:397
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:776 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline]
 nsim_dev_trap_report_work+0x654/0xb00 drivers/net/netdevsim/dev.c:851
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
 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>

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/23 02:00 linux-6.6.y 4fc00fe35d46 5b92003d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/12/29 04:08 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/02/05 06:16 linux-6.6.y 2cf6f68313dc ea10c935 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/10/25 07:05 linux-6.6.y 4a243110dc88 c0460fcd .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/08/10 16:04 linux-6.6.y 3a8ababb8b6a 32a0e5ed .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/06/25 22:50 linux-6.6.y 6282921b6825 26d77996 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/04/13 03:15 linux-6.6.y 8cee53b8eaeb 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/12/28 23:03 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/12/11 22:23 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
* Struck through repros no longer work on HEAD.