[v5.15] INFO: task hung in nfsd_svc

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 674f684f7c61 Linux 5.15.212
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=118816b9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=7048cf211f415c8fc042
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f55be2937b89/disk-674f684f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a19fb0ffc049/vmlinux-674f684f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/365d4529a007/bzImage-674f684f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7048cf...@syzkaller.appspotmail.com

INFO: task syz.4.138:4831 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.138 state:D stack:26736 pid: 4831 ppid: 4193 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11c3/0x4350 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xdf5/0x2400 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
nfsd_svc+0x60/0x9e0 fs/nfsd/nfssvc.c:785
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd6382a3e99
RSP: 002b:00007fd6364db028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd63852c090 RCX: 00007fd6382a3e99
RDX: 0000000000000002 RSI: 0000200000000100 RDI: 0000000000000005
RBP: 00007fd638339eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd63852c128 R14: 00007fd63852c090 R15: 00007ffee8fc1f08
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3952:
#0: ffff88802bbdd098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x594/0x1a50 drivers/tty/n_tty.c:2158
2 locks held by syz-executor/4192:
2 locks held by kworker/u4:5/4237:
3 locks held by syz.4.138/4827:
#0: ffff88801fb380f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
#1: ffff88807b14c460 (sb_writers#20){.+.+}-{0:0}, at: vfs_write+0x296/0xd70 fs/read_write.c:590
#2: ffffffff8c571728 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb3/0xb80 fs/nfsd/nfsctl.c:848
3 locks held by syz.4.138/4831:
#0: ffff88801fb1f9f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
#1: ffff88807b14c460 (sb_writers#20){.+.+}-{0:0}, at: vfs_write+0x296/0xd70 fs/read_write.c:590
#2: ffffffff8c571728 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x60/0x9e0 fs/nfsd/nfssvc.c:785
2 locks held by kworker/0:19/5936:
#0: ffff888016c72138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
#1: ffffc900036afd00 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
3 locks held by kworker/0:20/5938:
#0: ffff888016c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
#1: ffffc9000371fd00 ((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
#2: ffffffff8c3239e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
#2: ffffffff8c3239e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2d1/0x750 kernel/rcu/tree_exp.h:845

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

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 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe1b/0xe60 kernel/hung_task.c:369
kthread+0x42e/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4253 Comm: kworker/u4:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: bat_events batadv_nc_worker
RIP: 0010:check_preemption_disabled+0x60/0x110 lib/smp_processor_id.c:19
Code: 00 48 3b 4c 24 08 0f 85 c4 00 00 00 48 83 c4 10 5b 41 5e 41 5f 5d c3 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 <74> cc 65 4c 8b 3d b6 4a 42 76 41 f6 47 2f 04 74 0a 41 83 bf 10 04
RSP: 0018:ffffc900041afa88 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffff88802a339dc0 RCX: 0000000080000000
RDX: 0000000000000000 RSI: ffffffff8a2b39e0 RDI: ffffffff8a7a4200
RBP: ffffc900041afbd0 R08: ffffffff8d8b0def R09: 1ffffffff1b161bd
R10: dffffc0000000000 R11: fffffbfff1b161be R12: 1ffff92000835f64
R13: dffffc0000000000 R14: ffff88802a33a8ac R15: 0000000000000246
FS: 0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd472a9d000 CR3: 0000000071c49000 CR4: 00000000003506e0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000002
DR3: ffffffffefffff15 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
lockdep_recursion_inc kernel/locking/lockdep.c:431 [inline]
lock_release+0x15d/0x8a0 kernel/locking/lockdep.c:5642
rcu_read_unlock include/linux/rcupdate.h:773 [inline]
batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:416 [inline]
batadv_nc_worker+0x255/0x5c0 net/batman-adv/network-coding.c:723
process_one_work+0x867/0xff0 kernel/workqueue.c:2310
worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
kthread+0x42e/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>


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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc5c83b7f5f8 Linux 6.1.178
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=162691b9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=872c04466179833f
dashboard link: https://syzkaller.appspot.com/bug?extid=ff63c2da7c241c7f3492

compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:

disk image: https://storage.googleapis.com/syzbot-assets/96393e4697a3/disk-dc5c83b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0d4afce44fab/vmlinux-dc5c83b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4787e310d875/Image-dc5c83b7.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+ff63c2...@syzkaller.appspotmail.com

INFO: task syz.2.519:6460 blocked for more than 143 seconds.

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

task:syz.2.519 state:D stack:0 pid:6460 ppid:5649 flags:0x00000001
Call trace:
__switch_to+0x2f4/0x550 arch/arm64/kernel/process.c:555
context_switch kernel/sched/core.c:5246 [inline]
__schedule+0xdb4/0x1a6c kernel/sched/core.c:6563
schedule+0xc4/0x170 kernel/sched/core.c:6639
schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6698
__mutex_lock_common+0xb20/0x1f3c kernel/locking/mutex.c:679
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
nfsd_svc+0x74/0x948 fs/nfsd/nfssvc.c:783
write_threads+0x2b4/0x310 fs/nfsd/nfsctl.c:424
nfsctl_transaction_write+0x114/0x164 fs/nfsd/nfsctl.c:114
vfs_write+0x2a8/0x7c8 fs/read_write.c:582
ksys_write+0x12c/0x228 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Showing all locks held in the system:

1 lock held by rcu_tasks_kthre/12:
#0: ffff800015557db0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x40/0xc48 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffff8000155585d0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x40/0xc48 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
#0: ffff800015557440 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:349
3 locks held by kworker/1:2/1519:
#0: ffff0000d5fb3138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
#1: ffff800025197c40 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
#2: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
1 lock held by klogd/3929:
1 lock held by dhcpcd/3995:
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x64c/0xcc4 net/core/rtnetlink.c:6163
2 locks held by getty/4083:
#0: ffff0000d6825098 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
#1: ffff80002093b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x2e8/0xfa8 drivers/tty/n_tty.c:2198
3 locks held by kworker/u4:8/4451:
#0: ffff0000c0029138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
#1: ffff800021727c40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267
#2: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
3 locks held by syz.2.519/6456:
#0: ffff0000dc177768 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
#1: ffff0000d23c2460 (sb_writers#21){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
#2: ffff8000157e3f68 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xbc/0x9f0 fs/nfsd/nfsctl.c:846
3 locks held by syz.2.519/6460:
#0: ffff0000cb659c68 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x118/0x17c fs/file.c:1038
#1: ffff0000d23c2460 (sb_writers#21){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
#2: ffff8000157e3f68 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x74/0x948 fs/nfsd/nfssvc.c:783
2 locks held by kworker/u4:25/8452:
1 lock held by syz.8.995/9069:
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
2 locks held by syz.1.1006/9128:
#0: ffff0000e0225610 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
#0: ffff0000e0225610 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: __sock_release net/socket.c:653 [inline]
#0: ffff0000e0225610 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: sock_close+0x74/0x1ec net/socket.c:1400
#1: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
1 lock held by syz.5.1007/9135:
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x64c/0xcc4 net/core/rtnetlink.c:6163
1 lock held by syz.5.1007/9136:
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: __netlink_dump_start+0x104/0x694 net/netlink/af_netlink.c:2310
1 lock held by syz.4.1008/9143:
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x64c/0xcc4 net/core/rtnetlink.c:6163
3 locks held by syz.7.1012/9156:
#0: ffff800017a615b0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x28/0x50 net/netlink/genetlink.c:860
#1: ffff800017a613c8 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
#1: ffff800017a613c8 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0xec/0x600 net/netlink/genetlink.c:848
#2: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74
1 lock held by syz.7.1012/9157:
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x64c/0xcc4 net/core/rtnetlink.c:6163
1 lock held by syz.7.1012/9160:
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffff800017a04e48 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x64c/0xcc4 net/core/rtnetlink.c:6163

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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c5596480c50e Linux 6.6.145
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1034e499580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=3af7fc658946546571d0

compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:

disk image: https://storage.googleapis.com/syzbot-assets/eb5cda0a8020/disk-c5596480.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca05ff2fc502/vmlinux-c5596480.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6daf3255b985/bzImage-c5596480.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+3af7fc...@syzkaller.appspotmail.com

INFO: task syz.3.697:7640 blocked for more than 143 seconds.

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

task:syz.3.697 state:D stack:27912 pid:7640 ppid:5777 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6701
schedule+0xbd/0x170 kernel/sched/core.c:6775
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
nfsd_svc+0x65/0xab0 fs/nfsd/nfssvc.c:788
write_threads+0x393/0x510 fs/nfsd/nfsctl.c:417
nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
vfs_write+0x299/0x9a0 fs/read_write.c:582
ksys_write+0x151/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc6dd59de99
RSP: 002b:00007fc6db7d5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc6dd826090 RCX: 00007fc6dd59de99
RDX: 0000000000000002 RSI: 0000200000000140 RDI: 0000000000000004
RBP: 00007fc6dd633eaf R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007fc6dd826128 R14: 00007fc6dd826090 R15: 00007fff23472a68
</TASK>

Showing all locks held in the system:

1 lock held by khungtaskd/29:
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by kworker/u4:2/30:
10 locks held by kworker/0:2/172:
2 locks held by kworker/u4:9/3428:
2 locks held by kworker/u4:12/4292:
#0: ffff888017c71538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#0: ffff888017c71538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
#1: ffffc9000eb87d00 (connector_reaper_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#1: ffffc9000eb87d00 (connector_reaper_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
2 locks held by getty/5534:
#0: ffff88803197a0a0 (&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+0x428/0x1370 drivers/tty/n_tty.c:2217
2 locks held by syz-executor/5776:
#0: ffff88801fb740e0 (&type->s_umount_key#60){+.+.}-{3:3}, at: __super_lock fs/super.c:56 [inline]
#0: ffff88801fb740e0 (&type->s_umount_key#60){+.+.}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
#0: ffff88801fb740e0 (&type->s_umount_key#60){+.+.}-{3:3}, at: deactivate_super+0xa4/0xe0 fs/super.c:513
#1: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_shutdown_threads+0x53/0x1a0 fs/nfsd/nfssvc.c:638
2 locks held by kworker/1:4/5820:
3 locks held by syz.3.697/7637:
#0: ffff888023da4348 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88805ba2a418 (sb_writers#17){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
3 locks held by syz.3.697/7640:
#0: ffff88802671bc48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88805ba2a418 (sb_writers#17){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x65/0xab0 fs/nfsd/nfssvc.c:788
2 locks held by syz-executor/7939:
#0: ffff88802d8f80e0 (&type->s_umount_key#60){+.+.}-{3:3}, at: __super_lock fs/super.c:56 [inline]
#0: ffff88802d8f80e0 (&type->s_umount_key#60){+.+.}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
#0: ffff88802d8f80e0 (&type->s_umount_key#60){+.+.}-{3:3}, at: deactivate_super+0xa4/0xe0 fs/super.c:513
#1: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_shutdown_threads+0x53/0x1a0 fs/nfsd/nfssvc.c:638
3 locks held by syz.0.814/8227:
#0: ffff88802eaefc48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff888079a90418 (sb_writers#17){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
3 locks held by syz.5.815/8237:
#0: ffff88823bdb6ec8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff888027864418 (sb_writers#17){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
1 lock held by udevd/8404:
3 locks held by syz.7.845/8608:
#0: ffff8880213ecd48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88802c432418 (sb_writers#17){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: write_versions+0x96/0xe00 fs/nfsd/nfsctl.c:676
3 locks held by syz.7.845/8609:
#0: ffff88802deea0c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88802c432418 (sb_writers#17){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
3 locks held by syz.7.845/8610:
#0: ffff888025b78348 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88802c432418 (sb_writers#17){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e17a8 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x65/0xab0 fs/nfsd/nfssvc.c:788
1 lock held by syz.4.1069/9720:
#0: ffffffff8d137640 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x4c/0x530 kernel/rcu/tree.c:4089
1 lock held by syz.3.1068/9724:
2 locks held by dhcpcd-run-hook/9743:

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>

dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
watchdog+0xf59/0xfa0 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: 172 Comm: kworker/0:2 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026

Workqueue: usb_hub_wq hub_event
RIP: 0010:preempt_count_sub+0x0/0x160 kernel/sched/core.c:5869
Code: 03 38 c1 0f 8c 6e ff ff ff 48 c7 c7 60 b1 8c 8e e8 75 08 83 00 89 df e9 5b ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <f3> 0f 1e fa 55 53 48 bb 00 00 00 00 00 fc ff df 48 c7 c0 80 24 2f
RSP: 0000:ffffc90000006d10 EFLAGS: 00000246
RAX: ffffffff813bc0d3 RBX: ffffc90002df0001 RCX: ffff88801bbe3c00
RDX: 0000000000000100 RSI: ffffc90002df74c0 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffff88801bbe3c00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000100 R12: ffffc90002df74c0
R13: ffffc90000006de8 R14: ffffc90002df7508 R15: ffffc90000006df8
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

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

CR2: 00007f1946456010 CR3: 000000000cf32000 CR4: 00000000003506f0
Call Trace:
<IRQ>
unwind_next_frame+0x1d1b/0x2990 arch/x86/kernel/unwind_orc.c:672
arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
__kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
skb_kfree_head net/core/skbuff.c:946 [inline]
skb_free_head net/core/skbuff.c:958 [inline]
skb_release_data+0x609/0x7f0 net/core/skbuff.c:988
skb_release_all net/core/skbuff.c:1054 [inline]
__kfree_skb net/core/skbuff.c:1068 [inline]
consume_skb+0xb2/0x110 net/core/skbuff.c:1284
nft_synproxy_eval_v4+0x36b/0x4e0 net/netfilter/nft_synproxy.c:-1
nft_synproxy_do_eval+0x332/0x550 net/netfilter/nft_synproxy.c:140
expr_call_ops_eval net/netfilter/nf_tables_core.c:240 [inline]
nft_do_chain+0x44b/0x1620 net/netfilter/nf_tables_core.c:288
nft_do_chain_inet+0x29b/0x380 net/netfilter/nft_chain_filter.c:161
nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
nf_hook include/linux/netfilter.h:259 [inline]
NF_HOOK+0x21d/0x3b0 include/linux/netfilter.h:302
NF_HOOK+0x32d/0x3b0 include/linux/netfilter.h:304
__netif_receive_skb_one_core net/core/dev.c:5646 [inline]
__netif_receive_skb+0xcc/0x290 net/core/dev.c:5760
process_backlog+0x380/0x710 net/core/dev.c:6088
__napi_poll+0xbb/0x460 net/core/dev.c:6650
napi_poll net/core/dev.c:6717 [inline]
net_rx_action+0x65f/0xcc0 net/core/dev.c:6853
handle_softirqs+0x27d/0x820 kernel/softirq.c:578
__do_softirq kernel/softirq.c:612 [inline]
invoke_softirq kernel/softirq.c:452 [inline]
__irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:console_flush_all+0x883/0xcf0 arch/x86/include/asm/irqflags.h:-1
Code: ed 01 00 00 e8 be 81 1b 00 4d 85 ff 48 8b 5c 24 38 75 07 e8 af 81 1b 00 eb 06 e8 a8 81 1b 00 fb 49 bf 00 00 00 00 00 fc ff df <48> 8b 44 24 58 42 0f b6 04 38 84 c0 0f 85 2f 02 00 00 80 3b 01 0f
RSP: 0000:ffffc90002df6bc0 EFLAGS: 00000287
RAX: ffffffff816bf328 RBX: ffffc90002df6d3f RCX: 0000000000100000
RDX: ffffc9001882c000 RSI: 00000000000183f4 RDI: 00000000000183f5
RBP: ffffc90002df6d10 R08: ffffffff911eb507 R09: 1ffffffff223d6a0
R10: dffffc0000000000 R11: fffffbfff223d6a1 R12: ffffffff8d8cdf60
R13: 1ffffffff19f96d8 R14: ffffffff8d8cdfb8 R15: dffffc0000000000
console_unlock+0xad/0x350 kernel/printk/printk.c:3069
vprintk_emit+0x497/0x610 kernel/printk/printk.c:2341
dev_vprintk_emit+0x339/0x3f0 drivers/base/core.c:4970
dev_printk_emit+0xef/0x140 drivers/base/core.c:4981
_dev_info+0x11f/0x170 drivers/base/core.c:5039
usb_serial_device_remove+0x14d/0x1e0 drivers/usb/serial/bus.c:99
device_remove drivers/base/dd.c:626 [inline]
__device_release_driver drivers/base/dd.c:1351 [inline]
device_release_driver_internal+0x408/0x6f0 drivers/base/dd.c:1374
bus_remove_device+0x43b/0x520 drivers/base/bus.c:624
device_del+0x51f/0x910 drivers/base/core.c:3889
usb_serial_disconnect+0x296/0x4c0 drivers/usb/serial/usb-serial.c:1200
usb_unbind_interface+0x207/0x870 drivers/usb/core/driver.c:458
device_remove drivers/base/dd.c:628 [inline]
__device_release_driver drivers/base/dd.c:1351 [inline]
device_release_driver_internal+0x458/0x6f0 drivers/base/dd.c:1374
bus_remove_device+0x43b/0x520 drivers/base/bus.c:624
device_del+0x51f/0x910 drivers/base/core.c:3889
usb_disable_device+0x3ee/0x8a0 drivers/usb/core/message.c:1474
usb_disconnect+0x340/0x8a0 drivers/usb/core/hub.c:2315
hub_port_connect drivers/usb/core/hub.c:5369 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5669 [inline]
port_event drivers/usb/core/hub.c:5833 [inline]
hub_event+0x1d69/0x4a80 drivers/usb/core/hub.c:5915
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>