[v6.1] INFO: task hung in tun_chr_close (2)
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syzbot
Dec 30, 2025, 4:13:25 PM (2 days ago) 12/30/25
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: 50cbba13faa2 Linux 6.1.159
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=115892fc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6a5cbd268406bf43
dashboard link: https://syzkaller.appspot.com/bug?extid=4be8d52b2c93a6bef161
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b43fb8fc9816/disk-50cbba13.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ba3d5dc8928b/vmlinux-50cbba13.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2b4e001b3742/bzImage-50cbba13.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4be8d5...@syzkaller.appspotmail.com
INFO: task syz.9.1192:10452 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.9.1192 state:D stack:25440 pid:10452 ppid:10160 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
tun_detach drivers/net/tun.c:698 [inline]
tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3492
__fput+0x22c/0x920 fs/file_table.c:320
task_work_run+0x1ca/0x250 kernel/task_work.c:203
get_signal+0x11a6/0x1350 kernel/signal.c:2648
arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8e4fd8f749
RSP: 002b:00007ffde6eac328 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f8e4ffe7da0 RCX: 00007f8e4fd8f749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f8e4ffe7da0 R08: 000000000000022c R09: 0000001ee6eac61f
R10: 00007f8e4ffe7cb0 R11: 0000000000000246 R12: 0000000000079757
R13: 00007ffde6eac420 R14: ffffffffffffffff R15: 00007ffde6eac440
</TASK>
INFO: task syz.3.1194:10454 blocked for more than 145 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.1194 state:D stack:25440 pid:10454 ppid:10154 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
tun_detach drivers/net/tun.c:698 [inline]
tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3492
__fput+0x22c/0x920 fs/file_table.c:320
task_work_run+0x1ca/0x250 kernel/task_work.c:203
get_signal+0x11a6/0x1350 kernel/signal.c:2648
arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f375058f749
RSP: 002b:00007ffd354596f8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f37507e7da0 RCX: 00007f375058f749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f37507e7da0 R08: 0000000000000234 R09: 0000001e354599ef
R10: 00007f37507e7cb0 R11: 0000000000000246 R12: 000000000007a580
R13: 00007ffd354597f0 R14: ffffffffffffffff R15: 00007ffd35459810
</TASK>
Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8c92bab0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8c92c2d0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
3 locks held by kworker/1:0/22:
#0: ffff888017471938 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#1: ffffc900001c7d00 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#2: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: reg_check_chans_work+0x8b/0xd80 net/wireless/reg.c:2499
1 lock held by khungtaskd/27:
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
3 locks held by kworker/1:1/41:
#0: ffff88814c630538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#1: ffffc90000b27d00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#2: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x15/0x30 net/ipv6/addrconf.c:4672
1 lock held by klogd/3625:
2 locks held by getty/4027:
#0: ffff88814caf7098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41b/0x1380 drivers/tty/n_tty.c:2198
3 locks held by kworker/0:8/4391:
#0: ffff88814c630538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#1: ffffc90004c8fd00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#2: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x15/0x30 net/ipv6/addrconf.c:4672
3 locks held by kworker/u4:25/5857:
1 lock held by syz-executor/8970:
1 lock held by syz.9.1192/10452:
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:698 [inline]
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3492
3 locks held by syz.9.1192/10453:
1 lock held by syz.3.1194/10454:
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:698 [inline]
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3492
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 27 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+0x168/0x22e lib/dump_stack.c:106
nmi_cpu_backtrace+0x3f4/0x470 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
watchdog+0xeee/0xf30 kernel/hung_task.c:377
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 8970 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:lookup_chain_cache kernel/locking/lockdep.c:3718 [inline]
RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:3738 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:3793 [inline]
RIP: 0010:__lock_acquire+0x144c/0x7c50 kernel/locking/lockdep.c:5049
Code: 42 80 3c 00 00 74 12 4c 89 e7 e8 8f f5 6d 00 49 b8 00 00 00 00 00 fc ff df 49 8b 1c 24 48 85 db 0f 94 c0 48 83 c3 f8 0f 94 c1 <08> c1 4c 89 b4 24 90 00 00 00 0f 84 99 02 00 00 e8 0f a7 ff ff 48
RSP: 0018:ffffc90003217880 EFLAGS: 00000097
RAX: 1ffffffff20c5400 RBX: ffffffff908cb6a0 RCX: ffffffff81631b00
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff908c8250
RBP: ffffc90003217ad0 R08: dffffc0000000000 R09: fffffbfff211904b
R10: fffffbfff211904b R11: 1ffffffff211904a R12: ffffffff9062a0d8
R13: 00000000000000a3 R14: 1e40456c94acc51e R15: ffff88802a96a890
FS: 000055556bf0c500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f37507e6188 CR3: 000000005e4ff000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<TASK>
lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
_raw_spin_lock_irq+0x9f/0xe0 kernel/locking/spinlock.c:170
spin_lock_irq include/linux/spinlock.h:376 [inline]
__set_current_blocked+0xe7/0x240 kernel/signal.c:3058
__ia32_sys_rt_sigreturn+0x184/0x790 arch/x86/kernel/signal.c:673
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa11072b829
Code: 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 90 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 c7 c0 0f 00 00 00 0f 05 <0f> 1f 80 00 00 00 00 48 81 ec 48 01 00 00 49 89 d0 64 48 8b 04 25
RSP: 002b:00007ffc4028c180 EFLAGS: 00000293 ORIG_RAX: 000000000000000f
RAX: ffffffffffffffda RBX: 0000000000000154 RCX: 00007fa11072b829
RDX: 00007ffc4028c180 RSI: 00007ffc4028c2b0 RDI: 0000000000000011
RBP: 00007ffc4028c78c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000001388
R13: 00000000000927c0 R14: 000000000007788c R15: 00007ffc4028c7e0
</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.
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If the report is already addressed, let syzbot know by replying with:
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If you want to overwrite report's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
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If you want to undo deduplication, reply with:
#syz undup
syzbot found the following issue on:
HEAD commit: 50cbba13faa2 Linux 6.1.159
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=115892fc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6a5cbd268406bf43
dashboard link: https://syzkaller.appspot.com/bug?extid=4be8d52b2c93a6bef161
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b43fb8fc9816/disk-50cbba13.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ba3d5dc8928b/vmlinux-50cbba13.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2b4e001b3742/bzImage-50cbba13.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4be8d5...@syzkaller.appspotmail.com
INFO: task syz.9.1192:10452 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.9.1192 state:D stack:25440 pid:10452 ppid:10160 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
tun_detach drivers/net/tun.c:698 [inline]
tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3492
__fput+0x22c/0x920 fs/file_table.c:320
task_work_run+0x1ca/0x250 kernel/task_work.c:203
get_signal+0x11a6/0x1350 kernel/signal.c:2648
arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8e4fd8f749
RSP: 002b:00007ffde6eac328 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f8e4ffe7da0 RCX: 00007f8e4fd8f749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f8e4ffe7da0 R08: 000000000000022c R09: 0000001ee6eac61f
R10: 00007f8e4ffe7cb0 R11: 0000000000000246 R12: 0000000000079757
R13: 00007ffde6eac420 R14: ffffffffffffffff R15: 00007ffde6eac440
</TASK>
INFO: task syz.3.1194:10454 blocked for more than 145 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.1194 state:D stack:25440 pid:10454 ppid:10154 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
tun_detach drivers/net/tun.c:698 [inline]
tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3492
__fput+0x22c/0x920 fs/file_table.c:320
task_work_run+0x1ca/0x250 kernel/task_work.c:203
get_signal+0x11a6/0x1350 kernel/signal.c:2648
arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f375058f749
RSP: 002b:00007ffd354596f8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f37507e7da0 RCX: 00007f375058f749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f37507e7da0 R08: 0000000000000234 R09: 0000001e354599ef
R10: 00007f37507e7cb0 R11: 0000000000000246 R12: 000000000007a580
R13: 00007ffd354597f0 R14: ffffffffffffffff R15: 00007ffd35459810
</TASK>
Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8c92bab0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8c92c2d0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
3 locks held by kworker/1:0/22:
#0: ffff888017471938 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#1: ffffc900001c7d00 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#2: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: reg_check_chans_work+0x8b/0xd80 net/wireless/reg.c:2499
1 lock held by khungtaskd/27:
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
3 locks held by kworker/1:1/41:
#0: ffff88814c630538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#1: ffffc90000b27d00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#2: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x15/0x30 net/ipv6/addrconf.c:4672
1 lock held by klogd/3625:
2 locks held by getty/4027:
#0: ffff88814caf7098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41b/0x1380 drivers/tty/n_tty.c:2198
3 locks held by kworker/0:8/4391:
#0: ffff88814c630538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#1: ffffc90004c8fd00 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#2: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x15/0x30 net/ipv6/addrconf.c:4672
3 locks held by kworker/u4:25/5857:
1 lock held by syz-executor/8970:
1 lock held by syz.9.1192/10452:
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:698 [inline]
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3492
3 locks held by syz.9.1192/10453:
1 lock held by syz.3.1194/10454:
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:698 [inline]
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3492
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 27 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+0x168/0x22e lib/dump_stack.c:106
nmi_cpu_backtrace+0x3f4/0x470 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
watchdog+0xeee/0xf30 kernel/hung_task.c:377
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 8970 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:lookup_chain_cache kernel/locking/lockdep.c:3718 [inline]
RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:3738 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:3793 [inline]
RIP: 0010:__lock_acquire+0x144c/0x7c50 kernel/locking/lockdep.c:5049
Code: 42 80 3c 00 00 74 12 4c 89 e7 e8 8f f5 6d 00 49 b8 00 00 00 00 00 fc ff df 49 8b 1c 24 48 85 db 0f 94 c0 48 83 c3 f8 0f 94 c1 <08> c1 4c 89 b4 24 90 00 00 00 0f 84 99 02 00 00 e8 0f a7 ff ff 48
RSP: 0018:ffffc90003217880 EFLAGS: 00000097
RAX: 1ffffffff20c5400 RBX: ffffffff908cb6a0 RCX: ffffffff81631b00
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff908c8250
RBP: ffffc90003217ad0 R08: dffffc0000000000 R09: fffffbfff211904b
R10: fffffbfff211904b R11: 1ffffffff211904a R12: ffffffff9062a0d8
R13: 00000000000000a3 R14: 1e40456c94acc51e R15: ffff88802a96a890
FS: 000055556bf0c500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f37507e6188 CR3: 000000005e4ff000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<TASK>
lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
_raw_spin_lock_irq+0x9f/0xe0 kernel/locking/spinlock.c:170
spin_lock_irq include/linux/spinlock.h:376 [inline]
__set_current_blocked+0xe7/0x240 kernel/signal.c:3058
__ia32_sys_rt_sigreturn+0x184/0x790 arch/x86/kernel/signal.c:673
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa11072b829
Code: 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 90 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 c7 c0 0f 00 00 00 0f 05 <0f> 1f 80 00 00 00 00 48 81 ec 48 01 00 00 49 89 d0 64 48 8b 04 25
RSP: 002b:00007ffc4028c180 EFLAGS: 00000293 ORIG_RAX: 000000000000000f
RAX: ffffffffffffffda RBX: 0000000000000154 RCX: 00007fa11072b829
RDX: 00007ffc4028c180 RSI: 00007ffc4028c2b0 RDI: 0000000000000011
RBP: 00007ffc4028c78c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000001388
R13: 00000000000927c0 R14: 000000000007788c R15: 00007ffc4028c7e0
</TASK>
---
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