[v6.6] INFO: task hung in io_wq_put_and_exit

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6282921b6825 Linux 6.6.94
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=143d9b70580000
kernel config: https://syzkaller.appspot.com/x/.config?x=96da6b2210cda427
dashboard link: https://syzkaller.appspot.com/bug?extid=ea8018030af6aec75b1e
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17343f0c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a3bf0d8e22b2/disk-6282921b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d1d442f782d0/vmlinux-6282921b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a8378f4b7e1b/bzImage-6282921b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ea8018...@syzkaller.appspotmail.com

INFO: task syz.1.17:5975 blocked for more than 143 seconds.
Not tainted 6.6.94-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.17 state:D stack:25416 pid:5975 ppid:5901 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x14e2/0x4580 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_timeout+0x9b/0x280 kernel/time/timer.c:2143
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:1264 [inline]
io_wq_put_and_exit+0x2f3/0x660 io_uring/io-wq.c:1292
io_uring_clean_tctx+0x120/0x190 io_uring/tctx.c:204
io_uring_cancel_generic+0x5f8/0x6a0 io_uring/io_uring.c:3506
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:1023
get_signal+0x12fc/0x1400 kernel/signal.c:2902
arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0826f8e929
RSP: 002b:00007f0827e730e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f08271b5fa8 RCX: 00007f0826f8e929
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f08271b5fa8
RBP: 00007f08271b5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f08271b5fac
R13: 0000000000000000 R14: 00007ffe6461b8c0 R15: 00007ffe6461b9a8
</TASK>

Showing all locks held in the system:
3 locks held by kworker/0:0/8:
#0: ffff888017870938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#0: ffff888017870938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#1: ffffc900000d7d00 (deferred_process_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#1: ffffc900000d7d00 (deferred_process_work){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#2: ffffffff8dfaecc8 (rtnl_mutex){+.+.}-{3:3}, at: switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104
1 lock held by khungtaskd/28:
#0: ffffffff8cd2f760 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8cd2f760 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8cd2f760 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
5 locks held by kworker/u4:2/33:
4 locks held by kworker/u4:3/48:
3 locks held by kworker/u4:6/1080:
#0: ffff888017871538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#0: ffff888017871538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#1: ffffc90004bffd00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#1: ffffc90004bffd00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#2: ffffffff8dfaecc8 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:286
2 locks held by getty/5530:
#0: ffff88802d3a10a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000326b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
2 locks held by kworker/1:4/5888:
#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: ffffc900032e7d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#1: ffffc900032e7d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
3 locks held by kworker/1:5/5907:
#0: ffff88802c8a5538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#0: ffff88802c8a5538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#1: ffffc90003347d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#1: ffffc90003347d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#2: ffffffff8dfaecc8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xd0/0x14e0 net/ipv6/addrconf.c:4164
3 locks held by kworker/0:6/5960:
#0: ffff88802c8a5538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#0: ffff88802c8a5538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#1: ffffc90003587d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#1: ffffc90003587d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#2: ffffffff8dfaecc8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xd0/0x14e0 net/ipv6/addrconf.c:4164
1 lock held by syz-executor/6799:
#0: ffffffff8dfaecc8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:78 [inline]
#0: ffffffff8dfaecc8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x76f/0xf10 net/core/rtnetlink.c:6472

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

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Not tainted 6.6.94-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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: 4510 Comm: kworker/u4:8 Not tainted 6.6.94-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:stack_trace_consume_entry+0x1c/0x270 kernel/stacktrace.c:86
Code: e8 c9 d4 f1 08 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 55 41 57 41 56 41 55 41 54 53 48 83 ec 18 48 ba 00 00 00 00 00 fc ff df <4c> 8d 47 10 4c 89 c5 48 c1 ed 03 0f b6 44 15 00 84 c0 0f 85 04 01
RSP: 0018:ffffc9000ee375f8 EFLAGS: 00000292
RAX: ffffffff813210aa RBX: ffffc9000ee37700 RCX: ffff888030655a00
RDX: dffffc0000000000 RSI: ffffffff8157d235 RDI: ffffc9000ee37700
RBP: ffffc9000ee376d0 R08: ffff888030655a00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff8157d235
R13: 0000000000000000 R14: ffffffff81746190 R15: ffffc9000ee37648
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc6d77b7bac CR3: 000000000cb30000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
arch_stack_walk+0x138/0x190 arch/x86/kernel/stacktrace.c:27
stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
kasan_kmalloc include/linux/kasan.h:198 [inline]
__do_kmalloc_node mm/slab_common.c:1007 [inline]
__kmalloc_node_track_caller+0xb2/0x230 mm/slab_common.c:1027
kmalloc_reserve+0x117/0x260 net/core/skbuff.c:581
__alloc_skb+0x138/0x2c0 net/core/skbuff.c:650
alloc_skb include/linux/skbuff.h:1284 [inline]
nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:748 [inline]
nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline]
nsim_dev_trap_report_work+0x293/0xb00 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>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

syzbot suspects this issue could be fixed by backporting the following commit:

commit bcb0fda3c2da9fe4721d3e73d80e778c038e7d27
git tree: upstream
Author: Jens Axboe <ax...@kernel.dk>
Date: Wed Mar 5 21:03:34 2025 +0000

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

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10c536a2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=96da6b2210cda427
dashboard link: https://syzkaller.appspot.com/bug?extid=ea8018030af6aec75b1e

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17343f0c580000


Please keep in mind that other backports might be required as well.

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

For archival purposes, forwarding an incoming command email to
syzkaller...@googlegroups.com.

***

Subject: INFO: task hung in io_wq_put_and_exit
Author: sumanth...@yahoo.com

#syz test

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:

INFO: task hung in io_wq_put_and_exit

INFO: task syz.0.17:6922 blocked for more than 143 seconds.
Not tainted 6.6.101-syzkaller-dirty #0

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.0.17 state:D stack:25448 pid:6922 ppid:6618 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]

__schedule+0x14d2/0x44d0 kernel/sched/core.c:6700

schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_timeout+0x9b/0x280 kernel/time/timer.c:2143
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:3506
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

get_signal+0x12fc/0x1400 kernel/signal.c:2902
arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7f613db8ebe9
RSP: 002b:00007f613d1dd0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f613ddb6098 RCX: 00007f613db8ebe9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f613ddb6098
RBP: 00007f613ddb6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f613ddb6128 R14: 00007ffcaaf1cc70 R15: 00007ffcaaf1cd58
</TASK>
INFO: task syz.2.19:6939 blocked for more than 143 seconds.
Not tainted 6.6.101-syzkaller-dirty #0

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.2.19 state:D stack:25448 pid:6939 ppid:6623 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]

__schedule+0x14d2/0x44d0 kernel/sched/core.c:6700

schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_timeout+0x9b/0x280 kernel/time/timer.c:2143
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:3506
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

get_signal+0x12fc/0x1400 kernel/signal.c:2902
arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7f7cb7f8ebe9
RSP: 002b:00007f7cb8e330e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f7cb81b6098 RCX: 00007f7cb7f8ebe9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f7cb81b6098
RBP: 00007f7cb81b6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7cb81b6128 R14: 00007ffca20de8b0 R15: 00007ffca20de998

</TASK>

Showing all locks held in the system:

1 lock held by khungtaskd/29:
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by kworker/u4:4/58:
3 locks held by kworker/0:3/5431:

#0: ffff888017870938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#0: ffff888017870938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711

#1: ffffc90003677d00 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
#1: ffffc90003677d00 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
#2: ffff88805f4d3240 (&data->fib_lock){+.+.}-{3:3}, at: nsim_fib_event_work+0x26c/0x3170 drivers/net/netdevsim/fib.c:1491
2 locks held by getty/5552:
#0: ffff88803259a0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
2 locks held by syz-executor/8310:
#0: ffffffff8e020690 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1074
#1: ffffffff8dfbb888 (rtnl_mutex){+.+.}-{3:3}, at: nl80211_pre_doit+0x5f/0x930 net/wireless/nl80211.c:16515
4 locks held by syz-executor/8341:
#0: ffffffff8dfaea90 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x351/0x5e0 net/core/net_namespace.c:516
#1: ffffffff8dfbb888 (rtnl_mutex){+.+.}-{3:3}, at: ip_tunnel_init_net+0x2b4/0x770 net/ipv4/ip_tunnel.c:1117
#2: ffffffff8ce15d20 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:303 [inline]
#2: ffffffff8ce15d20 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook+0x2a/0x310 mm/slab.h:714
#3: ffff8880b8f3c458 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:558

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted 6.6.101-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025

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 1 to CPUs 0:

NMI backtrace for cpu 0

CPU: 0 PID: 1137 Comm: kworker/u4:8 Not tainted 6.6.101-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:get_current arch/x86/include/asm/current.h:41 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x60 kernel/kcov.c:215
Code: 00 00 f3 0f 1e fa 53 48 89 fb e8 13 00 00 00 48 8b 3d 8c f1 c4 0c 48 89 de 5b e9 63 75 56 00 cc cc cc f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0d 60 24 7e 7e 65 8b 15 61 24 7e 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc9000471fa88 EFLAGS: 00000202
RAX: ffffffff84501f48 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff8880234e1e00 RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000012 R08: ffff8880234e1e00 R09: 0000000000000003
R10: 000000000000002e R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff8880598da020 R15: 000000000000c731
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f2af27cfe9c CR3: 000000000cb30000 CR4: 00000000003506f0
Call Trace:
<TASK>
do_csum lib/checksum.c:83 [inline]
ip_fast_csum+0x1b8/0x2b0 lib/checksum.c:108
nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:771 [inline]
nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline]
nsim_dev_trap_report_work+0x583/0xb00 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>

Tested on:

commit: 3a8ababb Linux 6.6.101
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=122bc9a2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a2bd95b6de4839b7
dashboard link: https://syzkaller.appspot.com/bug?extid=ea8018030af6aec75b1e
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
patch: https://syzkaller.appspot.com/x/patch.diff?x=157bb434580000

[syzbot]

For archival purposes, forwarding an incoming command email to
syzkaller...@googlegroups.com.

***

Subject: Fw: INFO: task hung in io_wq_put_and_exit
Author: sumanth...@yahoo.com

#syz test

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:

INFO: task hung in io_wq_put_and_exit

INFO: task syz.1.18:6598 blocked for more than 143 seconds.

Not tainted 6.6.101-syzkaller-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.1.18 state:D stack:26472 pid:6598 ppid:6342 flags:0x00004000

RIP: 0033:0x7f7f2bb8ebe9
RSP: 002b:00007f7f2b1fe0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f7f2bdb6098 RCX: 00007f7f2bb8ebe9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f7f2bdb6098
RBP: 00007f7f2bdb6090 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f7f2bdb6128 R14: 00007fff320ef330 R15: 00007fff320ef418

</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8cd2fba0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633

2 locks held by getty/5541:
#0: ffff88802da410a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000328b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x425/0x1380 drivers/tty/n_tty.c:2217
2 locks held by kworker/u4:8/8278:

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

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted 6.6.101-syzkaller-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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: 2111 Comm: kworker/u4:6 Not tainted 6.6.101-syzkaller-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025

Workqueue: events_unbound cfg80211_wiphy_work
RIP: 0010:__sanitizer_cov_trace_pc+0x5c/0x60 kernel/kcov.c:234
Code: f8 15 00 00 83 fa 02 75 21 48 8b 91 00 16 00 00 48 8b 32 48 8d 7e 01 8b 89 fc 15 00 00 48 39 cf 73 08 48 89 3a 48 89 44 f2 08 <c3> 0f 1f 00 f3 0f 1e fa 48 8b 04 24 65 48 8b 15 00 24 7e 7e 65 8b
RSP: 0018:ffffc90004f26d30 EFLAGS: 00000293
RAX: ffffffff813aa3f0 RBX: 1ffff920009e4dc1 RCX: ffff888026388000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffffc90004f26e58 R08: ffffc90004f26ed0 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffc90004f26e08
R13: dffffc0000000000 R14: 0000000000000000 R15: ffffffff89c59282
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000555555b6b5c8 CR3: 000000000cb30000 CR4: 00000000003506e0
Call Trace:
<TASK>
unwind_next_frame+0x130/0x2970 arch/x86/kernel/unwind_orc.c:482
arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
kasan_save_stack+0x3e/0x60 mm/kasan/common.c:45
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
kvfree_call_rcu+0xee/0x780 kernel/rcu/tree.c:3452
cfg80211_update_known_bss+0x172/0x900 net/wireless/scan.c:-1
__cfg80211_bss_update+0x144/0x21f0 net/wireless/scan.c:1871
cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2981 [inline]
cfg80211_inform_bss_frame_data+0xaea/0x12b0 net/wireless/scan.c:3012
ieee80211_bss_info_update+0x70b/0x930 net/mac80211/scan.c:211
ieee80211_rx_bss_info net/mac80211/ibss.c:1124 [inline]
ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1613 [inline]
ieee80211_ibss_rx_queued_mgmt+0x17c9/0x2ac0 net/mac80211/ibss.c:1642
ieee80211_iface_process_skb net/mac80211/iface.c:1643 [inline]
ieee80211_iface_work+0x717/0xc70 net/mac80211/iface.c:1697
cfg80211_wiphy_work+0x225/0x260 net/wireless/core.c:437

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>


Tested on:

commit: 3a8ababb Linux 6.6.101
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=104a69a2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=a2bd95b6de4839b7
dashboard link: https://syzkaller.appspot.com/bug?extid=ea8018030af6aec75b1e
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

patch: https://syzkaller.appspot.com/x/patch.diff?x=15f3f434580000

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 5fa4793a2d2d Linux 6.6.119
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16c13bb4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=691a6769a86ac817
dashboard link: https://syzkaller.appspot.com/bug?extid=ea8018030af6aec75b1e
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13137c9a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14918422580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63699875f1dd/disk-5fa4793a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8506652fcb6f/vmlinux-5fa4793a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1b30ceed1710/bzImage-5fa4793a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ea8018...@syzkaller.appspotmail.com

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>


---