INFO: task hung in __fdget_pos

Status: upstream: reported on 2026/07/27 22:55
Reported-by: syzbot+8bb548076342d44fe137@syzkaller.appspotmail.com
First crash: 6d05h, last: 6d05h
▶ ▼ Similar bugs (16)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: task hung in __fdget_pos (3) origin:lts-only 1 syz, C done 1 577d 580d 3/3 fixed on 2025/02/05 14:14
linux-5.15 INFO: task hung in __fdget_pos (4) origin:lts-only 1 syz, C done 1 61d 428d 0/3 upstream: reported C repro on 2025/05/31 22:18
linux-6.1 INFO: task hung in __fdget_pos (2) 1 5 687d 721d 0/3 auto-obsoleted due to no activity on 2024/12/23 19:37
upstream INFO: task hung in __fdget_pos kernfs 1 1 3051d 3051d 0/29 closed as invalid on 2018/03/27 11:08
android-44 INFO: task hung in __fdget_pos 1 2 2871d 2884d 0/2 auto-closed as invalid on 2019/03/21 05:21
linux-6.1 INFO: task hung in __fdget_pos 1 1 1029d 1029d 0/3 auto-obsoleted due to no activity on 2024/01/16 13:13
android-49 INFO: task hung in __fdget_pos 1 22 2873d 3003d 0/3 auto-closed as invalid on 2019/03/20 03:41
upstream INFO: task hung in __fdget_pos (4) fs 1 syz, C error done 297 671d 1065d 0/29 auto-obsoleted due to no activity on 2025/07/22 08:19
upstream INFO: task hung in __fdget_pos (3) fs 1 3 1758d 1776d 0/29 auto-closed as invalid on 2022/01/07 10:38
android-414 INFO: task hung in __fdget_pos 1 1 2740d 2671d 0/1 auto-closed as invalid on 2019/07/30 11:39
linux-5.15 INFO: task hung in __fdget_pos (2) 1 2 828d 840d 0/3 auto-obsoleted due to no activity on 2024/08/04 06:39
linux-5.15 INFO: task hung in __fdget_pos 1 1 1220d 1220d 0/3 auto-obsoleted due to no activity on 2023/07/29 10:54
upstream INFO: task hung in __fdget_pos (2) fs 1 36 2763d 2988d 0/29 closed as dup on 2018/10/27 13:29
linux-5.15 INFO: task hung in __fdget_pos (3) 1 50 633d 721d 0/3 auto-obsoleted due to no activity on 2025/01/16 10:32
linux-6.1 INFO: task hung in __fdget_pos (4) origin:lts-only 1 syz, C inconclusive 7 52d 306d 0/3 upstream: reported C repro on 2025/09/30 10:05
upstream INFO: task can't die in __fdget_pos fs 1 1 1633d 1633d 0/29 auto-closed as invalid on 2022/04/12 09:48

Sample crash report:
INFO: task syz.2.7:5859 blocked for more than 157 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.7         state:D stack:28008 pid:5859  ppid:5776   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
 __fdget_pos+0x2a3/0x330 fs/file.c:1040
 fdget_pos include/linux/file.h:75 [inline]
 ksys_write+0x7b/0x260 fs/read_write.c:628
 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: 0033:0x7f66d7b9de99
RSP: 002b:00007f66d8a76028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f66d7e26090 RCX: 00007f66d7b9de99
RDX: 0000000000000002 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007f66d7c33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f66d7e26128 R14: 00007f66d7e26090 R15: 00007ffd9bdf6038
 </TASK>
INFO: task syz.2.7:5862 blocked for more than 158 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.7         state:D stack:28104 pid:5862  ppid:5776   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
 __fdget_pos+0x2a3/0x330 fs/file.c:1040
 fdget_pos include/linux/file.h:75 [inline]
 ksys_write+0x7b/0x260 fs/read_write.c:628
 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: 0033:0x7f66d7b9de99
RSP: 002b:00007f66d8a55028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f66d7e26180 RCX: 00007f66d7b9de99
RDX: 0000000000000002 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007f66d7c33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f66d7e26218 R14: 00007f66d7e26180 R15: 00007ffd9bdf6038
 </TASK>
INFO: task syz.3.17:5904 blocked for more than 158 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.17        state:D stack:27912 pid:5904  ppid:5773   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
 write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
 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: 0033:0x7f1fa2b9de99
RSP: 002b:00007f1fa3b02028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1fa2e25fa0 RCX: 00007f1fa2b9de99
RDX: 0000000000000009 RSI: 0000200000000140 RDI: 0000000000000003
RBP: 00007f1fa2c33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1fa2e26038 R14: 00007f1fa2e25fa0 R15: 00007ffd452c5408
 </TASK>
INFO: task syz.3.17:5905 blocked for more than 159 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.17        state:D stack:27912 pid:5905  ppid:5773   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: 0033:0x7f1fa2b9de99
RSP: 002b:00007f1fa3ae1028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1fa2e26090 RCX: 00007f1fa2b9de99
RDX: 0000000000000002 RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007f1fa2c33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1fa2e26128 R14: 00007f1fa2e26090 R15: 00007ffd452c5408
 </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/0:2/790:
 #0: ffff888017c72538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff888017c72538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #1: ffffc90003957d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc90003957d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
2 locks held by kworker/u4:7/2938:
 #0: ffff8881400cb538 ((wq_completion)xprtiod){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #0: ffff8881400cb538 ((wq_completion)xprtiod){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
 #1: ffffc9000bc17d00 ((work_completion)(&(&transport->connect_worker)->work)#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
 #1: ffffc9000bc17d00 ((work_completion)(&(&transport->connect_worker)->work)#2){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
1 lock held by syslogd/5121:
2 locks held by getty/5530:
 #0: ffff88814cb3e0a0 (&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
3 locks held by syz.2.7/5857:
 #0: ffff88802ecfcfc8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff888024310418 (sb_writers#13){.+.+}-{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 syz.2.7/5859:
 #0: ffff88802ecfcfc8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
1 lock held by syz.2.7/5862:
 #0: ffff88802ecfcfc8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
3 locks held by syz.3.17/5904:
 #0: ffff88807e72b9c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88807a5a2418 (sb_writers#13){.+.+}-{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.3.17/5905:
 #0: ffff88807ad02848 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88807a5a2418 (sb_writers#13){.+.+}-{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
3 locks held by syz.5.93/6297:
 #0: ffff88802e3d14c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff888053638418 (sb_writers#13){.+.+}-{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 syz.5.93/6301:
 #0: ffff88802e3d14c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
3 locks held by syz.6.122/6422:
 #0: ffff88802591a848 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88807b75e418 (sb_writers#13){.+.+}-{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.6.122/6424:
 #0: ffff88807c4619c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88807b75e418 (sb_writers#13){.+.+}-{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.6.122/6427:
 #0: ffff88802e63c0c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88807b75e418 (sb_writers#13){.+.+}-{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
3 locks held by syz.4.124/6442:
 #0: ffff888052d300c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88805fe56418 (sb_writers#13){.+.+}-{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.4.124/6444:
 #0: ffff888078d5a0c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88805fe56418 (sb_writers#13){.+.+}-{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.4.124/6446:
 #0: ffff88807a8f8d48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88805fe56418 (sb_writers#13){.+.+}-{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
3 locks held by syz.7.146/6640:
 #0: ffff888028a534c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88805f01a418 (sb_writers#13){.+.+}-{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.7.146/6642:
 #0: ffff88807d5f1c48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88805f01a418 (sb_writers#13){.+.+}-{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.7.146/6643:
 #0: ffff88802af22ac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88805f01a418 (sb_writers#13){.+.+}-{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
3 locks held by syz.8.151/6687:
 #0: ffff888063e8f748 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff888076caa418 (sb_writers#13){.+.+}-{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.3.173/7028:
 #0: ffff88807cf8cac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88807adfe418 (sb_writers#13){.+.+}-{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.3.173/7031:
 #0: ffff888028a3e0c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88807adfe418 (sb_writers#13){.+.+}-{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
3 locks held by syz.2.211/7045:
 #0: ffff8880253d1c48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88802c3dc418 (sb_writers#13){.+.+}-{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.2.211/7046:
 #0: ffff8880242125c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88802c3dc418 (sb_writers#13){.+.+}-{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.2.211/7049:
 #0: ffff888030b5e348 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88802c3dc418 (sb_writers#13){.+.+}-{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
3 locks held by syz.9.221/7081:
 #0: ffff88807e1d3c48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff8880521d4418 (sb_writers#13){.+.+}-{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.9.221/7086:
 #0: ffff88807e1d20c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff8880521d4418 (sb_writers#13){.+.+}-{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
3 locks held by syz.0.252/7178:
 #0: ffff88807ad039c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88802f55c418 (sb_writers#13){.+.+}-{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.0.252/7180:
 #0: ffff88807de78848 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88802f55c418 (sb_writers#13){.+.+}-{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
3 locks held by syz.1.265/7361:
 #0: ffff888078d22ac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff8880260c0418 (sb_writers#13){.+.+}-{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.1.265/7364:
 #0: ffff888052e140c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff8880260c0418 (sb_writers#13){.+.+}-{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.5.267/7376:
 #0: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
 #0: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3da/0x880 kernel/rcu/tree_exp.h:1004
3 locks held by syz-executor/7427:
 #0: ffff88803cc6ce70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:521 [inline]
 #0: ffff88803cc6ce70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x212/0x500 net/bluetooth/hci_core.c:2709
 #1: ffff88803cc6c0b8 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x552/0x1130 net/bluetooth/hci_sync.c:5317
 #2: ffffffff8e544288 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2016 [inline]
 #2: ffffffff8e544288 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0x99/0x220 net/bluetooth/hci_conn.c:2571
3 locks held by syz.6.285/7538:
 #0: ffff88802c82a848 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff888025076418 (sb_writers#13){.+.+}-{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.6.285/7541:
 #0: ffff88802c82aac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff888025076418 (sb_writers#13){.+.+}-{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
4 locks held by syz-executor/7637:
 #0: ffff88803d244e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:521 [inline]
 #0: ffff88803d244e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x212/0x500 net/bluetooth/hci_core.c:2709
 #1: ffff88803d2440b8 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x552/0x1130 net/bluetooth/hci_sync.c:5317
 #2: ffffffff8e544288 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2016 [inline]
 #2: ffffffff8e544288 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0x99/0x220 net/bluetooth/hci_conn.c:2571
 #3: ffff888058053338 (&conn->lock#2){+.+.}-{3:3}, at: l2cap_conn_del+0x7b/0x630 net/bluetooth/l2cap_core.c:1793
2 locks held by syz-executor/7659:
 #0: ffffffff8e3c9b10 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x342/0x5d0 net/core/net_namespace.c:516
 #1: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
 #1: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3da/0x880 kernel/rcu/tree_exp.h:1004

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

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: 7376 Comm: syz.5.267 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:26 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:check_preemption_disabled+0x56/0x110 lib/smp_processor_id.c:19
Code: 74 1f 65 48 8b 0c 25 28 00 00 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 46 cd 76 75 41 f6
RSP: 0018:ffffc9000b66f700 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff88802bb58adc RCX: 0000000080000000
RDX: 0000000000000000 RSI: ffffffff8acad8c0 RDI: ffffffff8b1d0660
RBP: ffffc9000b66f850 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: ffffffff81eae34c
R13: dffffc0000000000 R14: ffff88802bb58000 R15: 1ffff920016cdef4
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27efa77c50 CR3: 000000000cf32000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 lockdep_recursion_inc kernel/locking/lockdep.c:462 [inline]
 lock_release+0x15c/0x8c0 kernel/locking/lockdep.c:5773
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 vfree+0x1a7/0x340 mm/vmalloc.c:2868
 kcov_put kernel/kcov.c:438 [inline]
 kcov_close+0x2b/0x50 kernel/kcov.c:534
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x986/0x2530 kernel/exit.c:884
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1026
 get_signal+0x12a6/0x1390 kernel/signal.c:2903
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 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:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f51adf9de99
Code: Unable to access opcode bytes at 0x7f51adf9de6f.
RSP: 002b:00007f51ac1f6028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: 0000000000000038 RBX: 00007f51ae225fa0 RCX: 00007f51adf9de99
RDX: 0000000000000000 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007f51ae033eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f51ae226038 R14: 00007f51ae225fa0 R15: 00007ffcd7a70758
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/27 23:07 linux-6.6.y c5596480c50e aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in __fdget_pos
2026/07/27 22:55 linux-6.6.y c5596480c50e aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in __fdget_pos
* Struck through repros no longer work on HEAD.