[syzbot] [io-uring?] INFO: task hung in io_wq_put_and_exit (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 931e46dcbc7e Add linux-next specific files for 20250814
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16d26ba2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a286bd75352e92fa
dashboard link: https://syzkaller.appspot.com/bug?extid=4eb282331cab6d5b6588
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13d206f0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13e993a2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fb896162d550/disk-931e46dc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/45f6f857b82c/vmlinux-931e46dc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0f16e70143e1/bzImage-931e46dc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4eb282...@syzkaller.appspotmail.com

INFO: task syz-executor369:6499 blocked for more than 143 seconds.
Not tainted 6.17.0-rc1-next-20250814-syzkaller #0
Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor369 state:D stack:27984 pid:6499 tgid:6498 ppid:5865 task_flags:0x400548 flags:0x00024002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5357 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
__schedule_loop kernel/sched/core.c:7043 [inline]
schedule+0x165/0x360 kernel/sched/core.c:7058
schedule_timeout+0x9a/0x270 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common kernel/sched/completion.c:121 [inline]
wait_for_common kernel/sched/completion.c:132 [inline]
wait_for_completion+0x2bf/0x5d0 kernel/sched/completion.c:153
io_wq_exit_workers io_uring/io-wq.c:1327 [inline]
io_wq_put_and_exit+0x316/0x650 io_uring/io-wq.c:1355
io_uring_clean_tctx+0x11f/0x1a0 io_uring/tctx.c:203
io_uring_cancel_generic+0x6ca/0x7d0 io_uring/io_uring.c:3272
io_uring_files_cancel include/linux/io_uring.h:19 [inline]
do_exit+0x345/0x2300 kernel/exit.c:907
do_group_exit+0x21c/0x2d0 kernel/exit.c:1102
get_signal+0x1286/0x1340 kernel/signal.c:3034
arch_do_signal_or_restart+0x9a/0x750 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop+0x75/0x110 kernel/entry/common.c:40
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fec3779c659
RSP: 002b:00007fec37752218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007fec37823328 RCX: 00007fec3779c659
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fec37823328
RBP: 00007fec37823320 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fec377f0270
R13: 0000000000000000 R14: 0000200000000200 R15: 00007ffd3af7b848
</TASK>
INFO: lockdep is turned off.
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.17.0-rc1-next-20250814-syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
watchdog+0xf60/0xfa0 kernel/hung_task.c:495
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6811 Comm: iou-wrk-6807 Not tainted 6.17.0-rc1-next-20250814-syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:native_read_msr_safe arch/x86/include/asm/msr.h:121 [inline]
RIP: 0010:__rdmsr_safe_on_cpu+0x3c/0x130 arch/x86/lib/msr-smp.c:156
Code: bd 00 00 00 00 00 fc ff df e8 10 d2 bd fc 48 89 d8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 82 00 00 00 44 8b 23 44 89 e1 0f 32 <31> ed 49 89 c7 49 89 d6 0f 1f 44 00 00 e8 e2 d1 bd fc 49 c1 e6 20
RSP: 0018:ffffc90004e17428 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffffc90004e17600 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8be34be0 RDI: ffffc90004e17600
RBP: ffffc90004e17538 R08: ffffffff8fa3b137 R09: 1ffffffff1f47626
R10: dffffc0000000000 R11: ffffffff8501d3e0 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffffff8501d3e0 R15: 1ffff920009c2eb9
FS: 00007fec377526c0(0000) GS:ffff888125c0f000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000a89000 CR3: 0000000026df2000 CR4: 00000000003526f0
Call Trace:
<TASK>
csd_do_func kernel/smp.c:136 [inline]
generic_exec_single+0x237/0x500 kernel/smp.c:439
smp_call_function_single_async+0x79/0x110 kernel/smp.c:732
rdmsr_safe_on_cpu+0x127/0x230 arch/x86/lib/msr-smp.c:179
msr_read+0x14d/0x250 arch/x86/kernel/msr.c:66
loop_rw_iter+0x425/0x660 include/linux/uio.h:-1
io_iter_do_read io_uring/rw.c:830 [inline]
__io_read+0x1326/0x14f0 io_uring/rw.c:941
io_read+0x1c/0x60 io_uring/rw.c:1020
__io_issue_sqe+0x17e/0x4b0 io_uring/io_uring.c:1773
io_issue_sqe+0x165/0xfd0 io_uring/io_uring.c:1796
io_wq_submit_work+0x6e9/0xb90 io_uring/io_uring.c:1908
io_worker_handle_work+0x7cd/0x1180 io_uring/io-wq.c:650
io_wq_worker+0x42f/0xeb0 io_uring/io-wq.c:704
ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


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

[Jens Axboe]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git syztest

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in io_wq_exit_workers

INFO: task syz.2.600:7996 blocked for more than 143 seconds.
Not tainted syzkaller #0

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

task:syz.2.600 state:D stack:26824 pid:7996 tgid:7995 ppid:6341 task_flags:0x400548 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5260 [inline]
__schedule+0x1138/0x5ee0 kernel/sched/core.c:6867
__schedule_loop kernel/sched/core.c:6949 [inline]
schedule+0xe7/0x3a0 kernel/sched/core.c:6964
schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common+0x2fc/0x4e0 kernel/sched/completion.c:121
io_wq_exit_workers+0x3b7/0x8b0 io_uring/io-wq.c:1383
io_wq_put_and_exit+0xba/0x270 io_uring/io-wq.c:1414
io_uring_clean_tctx+0x10d/0x190 io_uring/tctx.c:203
io_uring_cancel_generic+0x69c/0x9a0 io_uring/cancel.c:651
io_uring_files_cancel include/linux/io_uring.h:19 [inline]
do_exit+0x2ce/0x2bd0 kernel/exit.c:911
do_group_exit+0xd3/0x2a0 kernel/exit.c:1112
get_signal+0x2671/0x26d0 kernel/signal.c:3034
arch_do_signal_or_restart+0x8f/0x7e0 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
exit_to_user_mode_loop+0x8c/0x540 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x4ee/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f22d238f749
RSP: 002b:00007f22d319b0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f22d25e5fa8 RCX: 00007f22d238f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f22d25e5fa8
RBP: 00007f22d25e5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f22d25e6038 R14: 00007ffdc1419da0 R15: 00007ffdc1419e88
</TASK>

Showing all locks held in the system:
3 locks held by kworker/0:0/9:
#0: ffff88813ff51948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x128d/0x1b20 kernel/workqueue.c:3232
#1:
ffffc900000e7c90 (deferred_process_work){+.+.}-{0:0}, at: process_one_work+0x914/0x1b20 kernel/workqueue.c:3233
#2: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104
3 locks held by kworker/1:0/24:
1 lock held by khungtaskd/31:
#0: ffffffff8e3c9620 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#0: ffffffff8e3c9620 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
#0: ffffffff8e3c9620 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775
2 locks held by kworker/u8:3/37:
#0: ffff88801c7fd148 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x128d/0x1b20 kernel/workqueue.c:3232
#1: ffffc90000ad7c90 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x914/0x1b20 kernel/workqueue.c:3233
5 locks held by kworker/u8:7/1041:
#0: ffff88801badc948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x128d/0x1b20 kernel/workqueue.c:3232
#1: ffffc90003a4fc90 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x914/0x1b20 kernel/workqueue.c:3233
#2: ffffffff9012bdd0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xad/0x830 net/core/net_namespace.c:670
#3: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline]
#3: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x7e9/0xab0 net/core/net_namespace.c:248
#4: ffffffff8e3d4d78 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x284/0x3c0 kernel/rcu/tree_exp.h:311
3 locks held by kworker/u8:9/1147:
#0: ffff88814cf76948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x128d/0x1b20 kernel/workqueue.c:3232
#1: ffffc90003f4fc90 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x914/0x1b20 kernel/workqueue.c:3233
#2: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
#2: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_verify_work+0x12/0x30 net/ipv6/addrconf.c:4734
3 locks held by kworker/u8:11/3526:
2 locks held by kworker/u8:12/3877:
#0: ffff88801c7fd148 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x128d/0x1b20 kernel/workqueue.c:3232
#1: ffffc9000c8b7c90 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x914/0x1b20 kernel/workqueue.c:3233
2 locks held by udevd/5186:
1 lock held by dhcpcd/5481:
#0: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
#0: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x26d/0x1f30 net/ipv4/devinet.c:1120
2 locks held by getty/5573:
#0: ffff8880367330a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc9000332e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x1510 drivers/tty/n_tty.c:2211
3 locks held by kworker/1:5/6331:
3 locks held by kworker/u8:16/6619:
#0: ffff88813ff69948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work+0x128d/0x1b20 kernel/workqueue.c:3232
#1: ffffc90003e1fc90 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x914/0x1b20 kernel/workqueue.c:3233
#2: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0x51/0xc0 net/core/link_watch.c:303
2 locks held by kworker/u8:18/6822:
#0: ffff88801c7fd148 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x128d/0x1b20 kernel/workqueue.c:3232
#1: ffffc90003507c90 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x914/0x1b20 kernel/workqueue.c:3233
7 locks held by kworker/1:10/7907:
2 locks held by kworker/u8:22/7948:
1 lock held by iou-wrk-7996/8005:
2 locks held by iou-wrk-8200/8202:
2 locks held by kworker/0:10/8282:
1 lock held by iou-wrk-8313/8318:
2 locks held by syz-executor/8492:
#0: ffffffff90890c48 (&ops->srcu#2){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:185 [inline]
#0: ffffffff90890c48 (&ops->srcu#2){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:277 [inline]
#0: ffffffff90890c48 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x113/0x2c0 net/core/rtnetlink.c:574
#1: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
#1: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
#1: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x5f6/0x1f50 net/core/rtnetlink.c:4071
2 locks held by syz-executor/8544:
#0: ffffffff8f4d9ea8 (
&ops->srcu
#2
){.+.+}-{0:0}
, at: srcu_lock_acquire include/linux/srcu.h:185 [inline]
, at: srcu_read_lock include/linux/srcu.h:277 [inline]
, at: rtnl_link_ops_get+0x113/0x2c0 net/core/rtnetlink.c:574
#1: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
#1: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
#1: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x5f6/0x1f50 net/core/rtnetlink.c:4071
1 lock held by syz-executor/8572:
#0: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
#0: ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: inet6_rtm_newaddr+0x4e4/0x1c50 net/ipv6/addrconf.c:5027
1 lock held by syz-executor/8691:
#0:
ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
ffffffff901428a8 (rtnl_mutex){+.+.}-{4:4}, at: inet_rtm_newaddr+0x30c/0x1540 net/ipv4/devinet.c:978
1 lock held by syz.4.861/8697:
1 lock held by syz.3.862/8699:

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

NMI backtrace for cpu 1

CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x133/0x180 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
watchdog+0xe66/0x1180 kernel/hung_task.c:515
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0

CPU: 0 UID: 0 PID: 1041 Comm: kworker/u8:7 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: netns cleanup_net
RIP: 0010:__trace_hardirqs_on_caller kernel/locking/lockdep.c:4350 [inline]
RIP: 0010:lockdep_hardirqs_on_prepare+0xc2/0x1b0 kernel/locking/lockdep.c:4410
Code: 48 89 83 08 0b 00 00 e8 1c 02 df 09 be 02 00 00 00 48 89 df 65 ff 05 e5 59 19 12 e8 b8 fe ff ff 85 c0 74 0a 8b 83 10 0b 00 00 <85> c0 75 24 48 c7 c7 45 97 aa 8d e8 ee 01 df 09 b8 ff ff ff ff 65
RSP: 0018:ffffc90000007d10 EFLAGS: 00000002
RAX: 0000000000000000 RBX: ffff88802819c980 RCX: 0000000000000002
RDX: 0000000000000000 RSI: ffff88802819d528 RDI: ffff88802819c980
RBP: 0000000000000202 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff9088cdd7 R11: ffff88802819d4b0 R12: 0000000000000038
R13: dffffc0000000000 R14: ffff888050975f80 R15: 1ffff92000000faa
FS: 0000000000000000(0000) GS:ffff8881248f1000(0000) knlGS:0000000000000000

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

CR2: 00002000006c6000 CR3: 0000000050306000 CR4: 00000000003526f0
Call Trace:
<IRQ>
trace_hardirqs_on+0x36/0x40 kernel/trace/trace_preemptirq.c:78
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
_raw_spin_unlock_irqrestore+0x52/0x80 kernel/locking/spinlock.c:194
debug_object_deactivate+0x1ec/0x3a0 lib/debugobjects.c:888
debug_rcu_head_unqueue kernel/rcu/rcu.h:248 [inline]
rcu_do_batch kernel/rcu/tree.c:2597 [inline]
rcu_core+0x72e/0x15f0 kernel/rcu/tree.c:2857
handle_softirqs+0x219/0x950 kernel/softirq.c:622
do_softirq kernel/softirq.c:523 [inline]
do_softirq+0xb2/0xf0 kernel/softirq.c:510
</IRQ>
<TASK>
__local_bh_enable_ip+0x100/0x120 kernel/softirq.c:450
spin_unlock_bh include/linux/spinlock.h:396 [inline]
addrconf_ifdown.isra.0+0x589/0x1b90 net/ipv6/addrconf.c:3907
addrconf_notify+0x220/0x19f0 net/ipv6/addrconf.c:3776
notifier_call_chain+0xbc/0x3e0 kernel/notifier.c:85
call_netdevice_notifiers_info+0xbe/0x110 net/core/dev.c:2243
call_netdevice_notifiers_extack net/core/dev.c:2281 [inline]
call_netdevice_notifiers net/core/dev.c:2295 [inline]
unregister_netdevice_many_notify+0xf81/0x2590 net/core/dev.c:12396
ops_exit_rtnl_list net/core/net_namespace.c:187 [inline]
ops_undo_list+0x8fc/0xab0 net/core/net_namespace.c:248
cleanup_net+0x41b/0x830 net/core/net_namespace.c:696
process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
process_scheduled_works kernel/workqueue.c:3340 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>


Tested on:

commit: ad6a6cb9 syztest
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git syztest
console output: https://syzkaller.appspot.com/x/log.txt?x=12502b9a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1859476832863c41
dashboard link: https://syzkaller.appspot.com/bug?extid=4eb282331cab6d5b6588
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.

[Jens Axboe]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git syztest

--
Jens Axboe

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to checkout kernel repo git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git/syztest: failed to run ["git" "checkout" "FETCH_HEAD" "--force"]: exit status 128


Tested on:

commit: [unknown

git tree: git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git syztest

kernel config: https://syzkaller.appspot.com/x/.config?x=a11e0f726bfb6765

dashboard link: https://syzkaller.appspot.com/bug?extid=4eb282331cab6d5b6588
compiler:

[Jens Axboe]

[syzbot]

[Jens Axboe]

Just to wrap this one up - there's a fairly lengthy explanation posted
here:

https://lore.kernel.org/io-uring/937c3e38-368e-43eb...@kernel.dk/

which details why this isn't really a bug, it's just slow exit due to
the odd huge reads (and number of them) syzbot queues up with io_uring
before exiting.

--
Jens Axboe

[Jens Axboe]

Let's see if syzbot is fixed again:

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git syztest

--
Jens Axboe

[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.1.135:6891 blocked for more than 143 seconds.

Not tainted syzkaller #0
Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.1.135 state:D stack:25688 pid:6891 tgid:6887 ppid:6342 task_flags:0x400548 flags:0x00080000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5260 [inline]

__schedule+0xfe4/0x5e10 kernel/sched/core.c:6867
__schedule_loop kernel/sched/core.c:6949 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:6964
schedule_timeout+0x1b2/0x280 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common+0x2e7/0x4c0 kernel/sched/completion.c:121
io_wq_exit_workers io_uring/io-wq.c:1325 [inline]
io_wq_put_and_exit+0x27b/0x8b0 io_uring/io-wq.c:1353
io_uring_clean_tctx+0x114/0x180 io_uring/tctx.c:203
io_uring_cancel_generic+0x7b9/0x810 io_uring/cancel.c:651
io_uring_files_cancel include/linux/io_uring.h:19 [inline]
do_exit+0x2be/0x2a30 kernel/exit.c:911
do_group_exit+0xd5/0x2a0 kernel/exit.c:1112
get_signal+0x1ec7/0x21e0 kernel/signal.c:3034
arch_do_signal_or_restart+0x91/0x7a0 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
exit_to_user_mode_loop+0x86/0x4b0 kernel/entry/common.c:75

__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]

do_syscall_64+0x4fe/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fee4299aef9
RSP: 002b:00007fee41fdd0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007fee42c06098 RCX: 00007fee4299aef9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fee42c06098
RBP: 00007fee42c06090 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007fee42c06128 R14: 00007fffcc8d1220 R15: 00007fffcc8d1308

</TASK>

Showing all locks held in the system:

1 lock held by khungtaskd/31:

#0: ffffffff8e3ca3a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#0: ffffffff8e3ca3a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
#0: ffffffff8e3ca3a0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
3 locks held by kworker/u8:4/60:
3 locks held by kworker/u8:6/640:
#0: ffff88813ff69948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work+0x11ae/0x1840 kernel/workqueue.c:3232
#1: ffffc90003767c98 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x927/0x1840 kernel/workqueue.c:3233
#2: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0x51/0xc0 net/core/link_watch.c:303
1 lock held by klogd/5176:
#0: ffff8880b853ac98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x29/0x130 kernel/sched/core.c:639
2 locks held by getty/5577:
#0: ffff88814e2a20a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x1500 drivers/tty/n_tty.c:2211
2 locks held by kworker/u8:16/6594:
#0: ffff8880b853ac98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x29/0x130 kernel/sched/core.c:639
#1: ffff8880b8524608 (psi_seq){-.-.}-{0:0}, at: psi_sched_switch kernel/sched/stats.h:225 [inline]
#1: ffff8880b8524608 (psi_seq){-.-.}-{0:0}, at: __schedule+0x2b6f/0x5e10 kernel/sched/core.c:6861
2 locks held by kworker/u8:17/6607:
#0: ffff88801d31e948 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x11ae/0x1840 kernel/workqueue.c:3232
#1: ffffc90004207c98 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x927/0x1840 kernel/workqueue.c:3233
2 locks held by kworker/u8:21/6678:
#0: ffff88801d31e948 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x11ae/0x1840 kernel/workqueue.c:3232
#1: ffffc9000465fc98 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x927/0x1840 kernel/workqueue.c:3233
2 locks held by syz.1.135/6891:
1 lock held by iou-wrk-6891/6895:
3 locks held by kworker/u8:23/6986:
#0: ffff88814cced948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x11ae/0x1840 kernel/workqueue.c:3232
#1: ffffc900053d7c98 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x927/0x1840 kernel/workqueue.c:3233
#2: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
#2: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_verify_work+0x12/0x30 net/ipv6/addrconf.c:4734
2 locks held by kworker/u8:24/7246:
#0: ffff88801d31e948 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x11ae/0x1840 kernel/workqueue.c:3232
#1: ffffc90004b3fc98 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x927/0x1840 kernel/workqueue.c:3233
1 lock held by iou-wrk-7337/7340:
2 locks held by kworker/u8:27/7716:
#0: ffff88801d31e948 ((wq_completion)iou_exit){+.+.}-{0:0}
, at: process_one_work+0x11ae/0x1840 kernel/workqueue.c:3232
#1: ffffc9000bea7c98 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x927/0x1840 kernel/workqueue.c:3233
3 locks held by kworker/u8:28/7784:
3 locks held by kworker/0:11/8074:
#0: ffff88813ff52948 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x11ae/0x1840 kernel/workqueue.c:3232
#1: ffffc9000d847c98 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work+0x927/0x1840 kernel/workqueue.c:3233
#2: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: reg_check_chans_work+0x91/0x10e0 net/wireless/reg.c:2453
3 locks held by syz-executor/8129:
#0: ffffffff8f4e5fe8 (&ops->srcu#2){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:185 [inline]
#0: ffffffff8f4e5fe8 (&ops->srcu#2){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:277 [inline]
#0: ffffffff8f4e5fe8 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x113/0x2c0 net/core/rtnetlink.c:574
#1: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
#1: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
#1: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8bb/0x2380 net/core/rtnetlink.c:4071
#2: ffffffff8e3d5db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343
1 lock held by dhcpcd/8197:
#0: ffff888053802a48 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1027 [inline]
#0: ffff888053802a48 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: __sock_release+0x86/0x260 net/socket.c:661
1 lock held by dhcpcd/8199:
#0: ffff888053803008 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1027 [inline]
#0: ffff888053803008 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: __sock_release+0x86/0x260 net/socket.c:661
2 locks held by dhcpcd/8202:
#0: ffff88805380bb88 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1027 [inline]
#0: ffff88805380bb88 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: __sock_release+0x86/0x260 net/socket.c:661
#1: ffffffff8e3d5db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343
1 lock held by dhcpcd/8205:
#0: ffff88807561b5c8 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1027 [inline]
#0: ffff88807561b5c8 (&sb->s_type->i_mutex_key#12){+.+.}-{4:4}, at: __sock_release+0x86/0x260 net/socket.c:661
1 lock held by dhcpcd/8208:
#0: ffff888026d0e260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1700 [inline]
#0: ffff888026d0e260 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3197
1 lock held by syz-executor/8219:
#0: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
#0: ffffffff90158368 (rtnl_mutex){+.+.}-{4:4}, at: inet_rtm_newaddr+0x30c/0x18b0 net/ipv4/devinet.c:978
2 locks held by syz.4.646/8226:
2 locks held by syz.5.647/8228:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026

Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]

dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x1d7/0x230 lib/nmi_backtrace.c:62

trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
__sys_info lib/sys_info.c:157 [inline]

sys_info+0x141/0x190 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
watchdog+0xcc3/0xfe0 kernel/hung_task.c:515
kthread+0x3b3/0x730 kernel/kthread.c:463
ret_from_fork+0x754/0xaf0 arch/x86/kernel/process.c:158

ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0

CPU: 0 UID: 0 PID: 8074 Comm: kworker/0:11 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026
Workqueue: wg-crypt-wg1 wg_packet_encrypt_worker
RIP: 0010:wg_queue_enqueue_per_peer_tx+0x155/0x500 drivers/net/wireguard/queueing.h:183
Code: 00 00 00 00 00 fc ff df 48 8b 2b 48 8d bd b8 05 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 69 03 00 00 48 8b 85 b8 05 00 00 <48> 8d bb 60 09 00 00 48 89 fa 48 89 44 24 08 48 c1 ea 03 48 b8 00
RSP: 0018:ffffc9000d847a90 EFLAGS: 00000246
RAX: ffff88806967b800 RBX: ffff88807f6c27a0 RCX: ffffffff8686ebc4
RDX: 1ffff1100643ba67 RSI: 0000000000000004 RDI: ffff8880321dd338
RBP: ffff8880321dcd80 R08: 0000000000000001 R09: ffffed100a3aea07
R10: ffff888051d7503b R11: caadeee402246cc6 R12: ffff888051d75000
R13: 0000000000000001 R14: ffff88807f6c2eb0 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8881248c5000(0000) knlGS:0000000000000000

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

CR2: 000020000017c000 CR3: 000000000e186000 CR4: 00000000003526f0
Call Trace:
<TASK>
wg_packet_encrypt_worker+0x7dc/0xbd0 drivers/net/wireguard/send.c:305
process_one_work+0x9c2/0x1840 kernel/workqueue.c:3257
process_scheduled_works kernel/workqueue.c:3340 [inline]
worker_thread+0x5da/0xe40 kernel/workqueue.c:3421
kthread+0x3b3/0x730 kernel/kthread.c:463
ret_from_fork+0x754/0xaf0 arch/x86/kernel/process.c:158

ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>


Tested on:

commit: c45d825f Merge branch 'io_uring-6.19' into syztest

git tree: git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git syztest

console output: https://syzkaller.appspot.com/x/log.txt?x=10fe3c44580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8f75eb998b5774eb
dashboard link: https://syzkaller.appspot.com/bug?extid=4eb282331cab6d5b6588
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44