[v6.6] INFO: task hung in nfsd4_write_time
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syzbot
Aug 4, 2026, 5:59:37 AM (4 days ago) Aug 4
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: aa0e49877a2e Linux 6.6.148
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14b8be32580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=b50a637aa9d545f63de7
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/f83b390cfc1f/disk-aa0e4987.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1d4bdb338edd/vmlinux-aa0e4987.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3f57c1d51ee3/bzImage-aa0e4987.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b50a63...@syzkaller.appspotmail.com
INFO: task syz.6.7173:28551 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.7173 state:D stack:27528 pid:28551 ppid:28194 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
nfsd4_write_time+0xae/0x740 fs/nfsd/nfsctl.c:984
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: 0033:0x7f3369b9e019
RSP: 002b:00007f336aadb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3369e25fa0 RCX: 00007f3369b9e019
RDX: 0000000000000003 RSI: 0000200000000470 RDI: 0000000000000003
RBP: 00007f3369c3500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3369e26038 R14: 00007f3369e25fa0 R15: 00007ffe6a5bf5c8
</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
3 locks held by kworker/u4:3/49:
#0: ffff88801a25d138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff88801a25d138 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffffc90000b9fd00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#1: ffffc90000b9fd00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#2: ffffffff8d137640 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x4c/0x530 kernel/rcu/tree.c:4089
2 locks held by getty/5535:
#0: ffff888031b520a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000325e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
3 locks held by kworker/1:4/5844:
#0: ffff8880b8e3c298 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x9c/0x130 kernel/sched/core.c:567
#1: ffff8880b8f28a00 (psi_seq){-.-.}-{0:0}, at: psi_sched_switch kernel/sched/stats.h:189 [inline]
#1: ffff8880b8f28a00 (psi_seq){-.-.}-{0:0}, at: __schedule+0x21d3/0x4660 kernel/sched/core.c:6696
#2: ffff8880b8f295d8 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:999
2 locks held by kworker/1:5/6525:
#0: ffff888017c72d38 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff888017c72d38 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffffc9000fd4fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#1: ffffc9000fd4fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
3 locks held by syz.5.7033/28018:
#0: ffff888069fea0c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88802faec418 (sb_writers#32){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x65/0xab0 fs/nfsd/nfssvc.c:788
3 locks held by kworker/1:1/28296:
#0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffffc9000336fd00 (free_ipc_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#1: ffffc9000336fd00 (free_ipc_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#2: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:292 [inline]
#2: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x306/0x880 kernel/rcu/tree_exp.h:1004
2 locks held by kworker/0:2/28432:
#0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffff8880b8e28a00 (psi_seq){-.-.}-{0:0}, at: psi_sched_switch kernel/sched/stats.h:189 [inline]
#1: ffff8880b8e28a00 (psi_seq){-.-.}-{0:0}, at: __schedule+0x21d3/0x4660 kernel/sched/core.c:6696
3 locks held by syz.6.7173/28551:
#0: ffff88804e564ac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff8880612a4418 (sb_writers#32){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: nfsd4_write_time+0xae/0x740 fs/nfsd/nfsctl.c:984
4 locks held by syz-executor/29756:
#0: ffff88804fc30e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:521 [inline]
#0: ffff88804fc30e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x212/0x500 net/bluetooth/hci_core.c:2709
#1: ffff88804fc300b8 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x552/0x1130 net/bluetooth/hci_sync.c:5326
#2: ffffffff8e543f48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2016 [inline]
#2: ffffffff8e543f48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0x99/0x220 net/bluetooth/hci_conn.c:2571
#3: ffff8880636e6338 (&conn->lock#2){+.+.}-{3:3}, at: l2cap_conn_del+0x7b/0x630 net/bluetooth/l2cap_core.c:1793
3 locks held by syz.8.7513/30022:
#0: ffff88803b704e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:521 [inline]
#0: ffff88803b704e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x212/0x500 net/bluetooth/hci_core.c:2709
#1: ffff88803b7040b8 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x552/0x1130 net/bluetooth/hci_sync.c:5326
#2: ffffffff8e543f48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2016 [inline]
#2: ffffffff8e543f48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0x99/0x220 net/bluetooth/hci_conn.c:2571
1 lock held by rm/30044:
=============================================
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 07/24/2026
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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6654 Comm: kworker/1:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_power_efficient wg_ratelimiter_gc_entries
RIP: 0010:check_region_inline mm/kasan/generic.c:-1 [inline]
RIP: 0010:kasan_check_range+0x12/0x290 mm/kasan/generic.c:187
Code: 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 cc cc cc cc cc cc cc cc 66 0f 1f 00 b0 01 48 85 f6 0f 84 b4 01 00 00 55 41 57 <41> 56 41 55 41 54 53 4c 8d 04 37 49 39 f8 0f 82 13 02 00 00 49 89
RSP: 0018:ffffc900038e7788 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 000000000000070e RCX: ffffffff81689802
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff911eb5e0
RBP: ffffc900038e79e8 R08: dffffc0000000000 R09: 1ffffffff223d6bc
R10: dffffc0000000000 R11: fffffbfff223d6bd R12: 0000000000000000
R13: ffff888074503c00 R14: ffffffff90baee50 R15: ffff888074504750
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa945be2286 CR3: 000000000cf32000 CR4: 00000000003506e0
Call Trace:
<TASK>
instrument_atomic_read include/linux/instrumented.h:68 [inline]
_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
__lock_acquire+0xd92/0x7d80 kernel/locking/lockdep.c:5107
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
wg_ratelimiter_gc_entries+0x5d/0x450 drivers/net/wireguard/ratelimiter.c:63
process_one_work kernel/workqueue.c:2657 [inline]
process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
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.
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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: aa0e49877a2e Linux 6.6.148
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14b8be32580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=b50a637aa9d545f63de7
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/f83b390cfc1f/disk-aa0e4987.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1d4bdb338edd/vmlinux-aa0e4987.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3f57c1d51ee3/bzImage-aa0e4987.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b50a63...@syzkaller.appspotmail.com
INFO: task syz.6.7173:28551 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.7173 state:D stack:27528 pid:28551 ppid:28194 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
nfsd4_write_time+0xae/0x740 fs/nfsd/nfsctl.c:984
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: 0033:0x7f3369b9e019
RSP: 002b:00007f336aadb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3369e25fa0 RCX: 00007f3369b9e019
RDX: 0000000000000003 RSI: 0000200000000470 RDI: 0000000000000003
RBP: 00007f3369c3500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3369e26038 R14: 00007f3369e25fa0 R15: 00007ffe6a5bf5c8
</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
3 locks held by kworker/u4:3/49:
#0: ffff88801a25d138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff88801a25d138 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffffc90000b9fd00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#1: ffffc90000b9fd00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#2: ffffffff8d137640 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x4c/0x530 kernel/rcu/tree.c:4089
2 locks held by getty/5535:
#0: ffff888031b520a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000325e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
3 locks held by kworker/1:4/5844:
#0: ffff8880b8e3c298 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x9c/0x130 kernel/sched/core.c:567
#1: ffff8880b8f28a00 (psi_seq){-.-.}-{0:0}, at: psi_sched_switch kernel/sched/stats.h:189 [inline]
#1: ffff8880b8f28a00 (psi_seq){-.-.}-{0:0}, at: __schedule+0x21d3/0x4660 kernel/sched/core.c:6696
#2: ffff8880b8f295d8 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x123/0x270 kernel/time/timer.c:999
2 locks held by kworker/1:5/6525:
#0: ffff888017c72d38 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff888017c72d38 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffffc9000fd4fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#1: ffffc9000fd4fd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
3 locks held by syz.5.7033/28018:
#0: ffff888069fea0c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88802faec418 (sb_writers#32){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_svc+0x65/0xab0 fs/nfsd/nfssvc.c:788
3 locks held by kworker/1:1/28296:
#0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffffc9000336fd00 (free_ipc_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#1: ffffc9000336fd00 (free_ipc_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#2: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:292 [inline]
#2: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x306/0x880 kernel/rcu/tree_exp.h:1004
2 locks held by kworker/0:2/28432:
#0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff888017c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffff8880b8e28a00 (psi_seq){-.-.}-{0:0}, at: psi_sched_switch kernel/sched/stats.h:189 [inline]
#1: ffff8880b8e28a00 (psi_seq){-.-.}-{0:0}, at: __schedule+0x21d3/0x4660 kernel/sched/core.c:6696
3 locks held by syz.6.7173/28551:
#0: ffff88804e564ac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff8880612a4418 (sb_writers#32){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
#2: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: nfsd4_write_time+0xae/0x740 fs/nfsd/nfsctl.c:984
4 locks held by syz-executor/29756:
#0: ffff88804fc30e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:521 [inline]
#0: ffff88804fc30e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x212/0x500 net/bluetooth/hci_core.c:2709
#1: ffff88804fc300b8 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x552/0x1130 net/bluetooth/hci_sync.c:5326
#2: ffffffff8e543f48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2016 [inline]
#2: ffffffff8e543f48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0x99/0x220 net/bluetooth/hci_conn.c:2571
#3: ffff8880636e6338 (&conn->lock#2){+.+.}-{3:3}, at: l2cap_conn_del+0x7b/0x630 net/bluetooth/l2cap_core.c:1793
3 locks held by syz.8.7513/30022:
#0: ffff88803b704e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:521 [inline]
#0: ffff88803b704e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x212/0x500 net/bluetooth/hci_core.c:2709
#1: ffff88803b7040b8 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x552/0x1130 net/bluetooth/hci_sync.c:5326
#2: ffffffff8e543f48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2016 [inline]
#2: ffffffff8e543f48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0x99/0x220 net/bluetooth/hci_conn.c:2571
1 lock held by rm/30044:
=============================================
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 07/24/2026
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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6654 Comm: kworker/1:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_power_efficient wg_ratelimiter_gc_entries
RIP: 0010:check_region_inline mm/kasan/generic.c:-1 [inline]
RIP: 0010:kasan_check_range+0x12/0x290 mm/kasan/generic.c:187
Code: 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 cc cc cc cc cc cc cc cc 66 0f 1f 00 b0 01 48 85 f6 0f 84 b4 01 00 00 55 41 57 <41> 56 41 55 41 54 53 4c 8d 04 37 49 39 f8 0f 82 13 02 00 00 49 89
RSP: 0018:ffffc900038e7788 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 000000000000070e RCX: ffffffff81689802
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff911eb5e0
RBP: ffffc900038e79e8 R08: dffffc0000000000 R09: 1ffffffff223d6bc
R10: dffffc0000000000 R11: fffffbfff223d6bd R12: 0000000000000000
R13: ffff888074503c00 R14: ffffffff90baee50 R15: ffff888074504750
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa945be2286 CR3: 000000000cf32000 CR4: 00000000003506e0
Call Trace:
<TASK>
instrument_atomic_read include/linux/instrumented.h:68 [inline]
_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
__lock_acquire+0xd92/0x7d80 kernel/locking/lockdep.c:5107
lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
wg_ratelimiter_gc_entries+0x5d/0x450 drivers/net/wireguard/ratelimiter.c:63
process_one_work kernel/workqueue.c:2657 [inline]
process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
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.
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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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If you want to undo deduplication, reply with:
#syz undup
syzbot
Aug 6, 2026, 1:17:26 PM (yesterday) Aug 6
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: fb28aa725e05 Linux 6.1.180
syzbot found the following issue on:
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15ab77b9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=d4b0d555b9afa7942416
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/9a6fe2a54d0f/disk-fb28aa72.raw.xz
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
vmlinux: https://storage.googleapis.com/syzbot-assets/742b23a1d931/vmlinux-fb28aa72.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b3f257c16d2e/bzImage-fb28aa72.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
INFO: task syz.5.1151:8318 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.1151 state:D stack:27088 pid:8318 ppid:5437 flags:0x00004004
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5246 [inline]
__schedule+0x107f/0x4030 kernel/sched/core.c:6563
schedule+0xb9/0x180 kernel/sched/core.c:6639
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6698
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x548/0xae0 kernel/locking/mutex.c:747
nfsd4_write_time+0xa4/0x330 fs/nfsd/nfsctl.c:980
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x2dc/0x9a0 fs/read_write.c:582
ksys_write+0x14d/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fde15b9e0d9
RSP: 002b:00007fde13dd5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fde15e26090 RCX: 00007fde15b9e0d9
RDX: 0000000000000002 RSI: 0000200000000140 RDI: 0000000000000004
RBP: 00007fde15c35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fde15e26128 R14: 00007fde15e26090 R15: 00007fff8f516fa8
</TASK>
Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
Showing all locks held in the system:
#0: ffffffff8cb2e4f0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8cb2ed10 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6527
2 locks held by getty/4028:
#0: ffff88814cd73098 (&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+0x41e/0x1360 drivers/tty/n_tty.c:2198
1 lock held by syz-executor/4258:
#0: ffff8880b8e3ad18 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x25/0x130 kernel/sched/core.c:538
2 locks held by kworker/0:5/4317:
#0: ffff888017472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc90004157d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
3 locks held by kworker/0:12/4566:
#0: ffff888017470938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc90004dbfd00 ((work_completion)(&pwq->unbound_release_work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#2: ffffffff8cb33838 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
#2: ffffffff8cb33838 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2ec/0x890 kernel/rcu/tree_exp.h:962
3 locks held by syz.5.1151/8315:
#0: ffff888078fcefe8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2ae/0x360 fs/file.c:1038
#1: ffff888068958460 (sb_writers#16){.+.+}-{0:0}, at: vfs_write+0x270/0x9a0 fs/read_write.c:580
#2: ffffffff8cdcce08 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb3/0xb80 fs/nfsd/nfsctl.c:846
3 locks held by syz.5.1151/8318:
#0: ffff888017750368 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2ae/0x360 fs/file.c:1038
#1: ffff888068958460 (sb_writers#16){.+.+}-{0:0}, at: vfs_write+0x270/0x9a0 fs/read_write.c:580
#2: ffffffff8cdcce08 (nfsd_mutex){+.+.}-{3:3}, at: nfsd4_write_time+0xa4/0x330 fs/nfsd/nfsctl.c:980
3 locks held by syz.8.1964/11276:
#0: ffff88802499a0e8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2ae/0x360 fs/file.c:1038
#1: ffff88807918e460 (sb_writers#16){.+.+}-{0:0}, at: vfs_write+0x270/0x9a0 fs/read_write.c:580
#2: ffffffff8cdcce08 (nfsd_mutex){+.+.}-{3:3}, at: write_versions+0x90/0xbb0 fs/nfsd/nfsctl.c:681
3 locks held by syz.8.1964/11278:
#0: ffff888027e84868 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2ae/0x360 fs/file.c:1038
#1: ffff88807918e460 (sb_writers#16){.+.+}-{0:0}, at: vfs_write+0x270/0x9a0 fs/read_write.c:580
#2: ffffffff8cdcce08 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb3/0xb80 fs/nfsd/nfsctl.c:846
2 locks held by syz-executor/11719:
#0: ffff88804d54e0e0 (&type->s_umount_key#57){++++}-{3:3}, at: deactivate_super+0xa0/0xd0 fs/super.c:362
#1: ffffffff8cb33838 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:323 [inline]
#1: ffffffff8cb33838 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3c0/0x890 kernel/rcu/tree_exp.h:962
2 locks held by sed/12906:
=============================================
NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
Call Trace:
<TASK>
nmi_cpu_backtrace+0x3e6/0x460 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+0xf0e/0xf50 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6241 Comm: kworker/u4:8 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x4/0x60 kernel/kcov.c:215
Code: 00 00 00 00 00 90 53 48 89 fb e8 17 00 00 00 48 8b 3d 00 df 9e 0c 48 89 de 5b e9 77 62 50 00 00 00 cc cc 00 00 cc 48 8b 04 24 <65> 48 8b 0d 14 41 80 7e 65 8b 15 15 41 80 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc900037efac0 EFLAGS: 00000283
RAX: ffffffff81d373e1 RBX: ffffffff96c90790 RCX: 0000000000000000
RDX: ffff88802aecbc00 RSI: 00000000000000aa RDI: 00000000000000aa
RBP: ffff88823bc866e5 R08: ffffffff96cdc327 R09: 1ffffffff2d9b864
R10: dffffc0000000000 R11: fffffbfff2d9b865 R12: ffff88823bc86f00
R13: ffff88823bc86000 R14: dffffc0000000000 R15: 00000000000000aa
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f54580368 CR3: 000000000c88e000 CR4: 00000000003506f0
Call Trace:
<TASK>
for_each_canary mm/kfence/core.c:345 [inline]
kfence_guarded_free+0x301/0x7b0 mm/kfence/core.c:501
do_slab_free mm/slub.c:3641 [inline]
slab_free mm/slub.c:3688 [inline]
kmem_cache_free+0x199/0x2a0 mm/slub.c:3709
nsim_dev_trap_report drivers/net/netdevsim/dev.c:821 [inline]
nsim_dev_trap_report_work+0x71f/0xa80 drivers/net/netdevsim/dev.c:851
process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
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