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: 200d, last: 12d
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 68 3d21h 146d 0/29 upstream: reported C repro on 2025/08/18 08:05
linux-5.15 INFO: task hung in io_wq_put_and_exit 1 1 671d 671d 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 995d 1390d 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 1525d 1586d 20/29 fixed on 2021/11/10 00:50
upstream INFO: task hung in io_wq_put_and_exit (2) fs 1 22 1493d 1522d 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 153d 172d 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 219d 449d 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.0.17:5924 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:24368 pid:5924  ppid:5875   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x9b/0x280 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+0x2bd/0x590 kernel/sched/completion.c:148
 io_wq_exit_workers io_uring/io-wq.c:1266 [inline]
 io_wq_put_and_exit+0x2f3/0x660 io_uring/io-wq.c:1294
 io_uring_clean_tctx+0x120/0x190 io_uring/tctx.c:204
 io_uring_cancel_generic+0x5f8/0x6a0 io_uring/io_uring.c:3507
 io_uring_files_cancel include/linux/io_uring.h:69 [inline]
 do_exit+0x5a7/0x23c0 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:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f22a338f749
RSP: 002b:00007fff237899d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f22a338f749
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000523789acf R09: 00007f22a35b4280
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f22a35b4280 R14: 0000000000000003 R15: 00007fff23789a90
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by kworker/u4:4/60:
2 locks held by getty/5529:
 #0: ffff88802c8bd0a0 (&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+0x425/0x1380 drivers/tty/n_tty.c:2217
2 locks held by kworker/0:5/5923:
 #0: ffff888017872538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #0: ffff888017872538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #1: ffffc90003047d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #1: ffffc90003047d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
2 locks held by syz-executor/6178:
 #0: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
 #0: ffffffff8dfb5448 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x76f/0xf10 net/core/rtnetlink.c:6469
 #1: ffffffff8cd358f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
 #1: ffffffff8cd358f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x360/0x830 kernel/rcu/tree_exp.h:1004
2 locks held by dhcpcd/6187:
 #0: ffff888073ee6e20 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
 #0: ffff888073ee6e20 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:658 [inline]
 #0: ffff888073ee6e20 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x9b/0x230 net/socket.c:1421
 #1: ffffffff8cd358f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:292 [inline]
 #1: ffffffff8cd358f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x448/0x830 kernel/rcu/tree_exp.h:1004

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

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 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x39b/0x3d0 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+0xf41/0xf80 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: 1114 Comm: kworker/u4:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:find_stack lib/stackdepot.c:349 [inline]
RIP: 0010:__stack_depot_save+0x149/0x630 lib/stackdepot.c:390
Code: e2 c1 c2 04 29 d1 31 c8 c1 c1 0e 29 c8 41 31 c4 c1 c0 18 41 29 c4 48 8b 35 fc e1 c8 12 8b 2d f2 e1 c8 12 44 21 e5 4c 8b 2c ee <4d> 85 ed 74 33 44 89 f0 eb 09 4d 8b 6d 00 4d 85 ed 74 25 45 39 65
RSP: 0018:ffffc9000475f758 EFLAGS: 00000202
RAX: 00000000002d5c67 RBX: ffffc9000475f7b0 RCX: 00000000279dc8e2
RDX: 000000001ebfaf9e RSI: ffff88823b400000 RDI: 0000000000000000
RBP: 00000000000a4192 R08: 00000000642e3a18 R09: 000000005a7f0e92
R10: 0000000000000001 R11: 0000000000000000 R12: 00000000cc8a4192
R13: ffff888026b3b570 R14: 000000000000000b R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe45d317d60 CR3: 000000000cb30000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x5f/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 kmem_cache_free+0xf8/0x280 mm/slub.c:3852
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:821 [inline]
 nsim_dev_trap_report_work+0x76f/0xb00 drivers/net/netdevsim/dev.c:851
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 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 (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
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
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.