INFO: task hung in vcs_open

Status: upstream: reported on 2026/10/31 05:40
Reported-by: syzbot+10e991b915314ea4078f@syzkaller.appspotmail.com
First crash: 3d19h, last: 3d19h
▶ ▼ Similar bugs (15)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in vcs_open (5) serial 1 2 1338d 1342d 0/29 auto-obsoleted due to no activity on 2023/06/04 04:45
upstream INFO: task hung in vcs_open (9) kernel 1 11 540d 705d 0/29 auto-obsoleted due to no activity on 2025/08/10 23:55
upstream INFO: task hung in vcs_open (3) serial 1 1 2081d 2081d 0/29 auto-closed as invalid on 2021/05/22 19:06
upstream INFO: task hung in vcs_open serial 1 32 2251d 2384d 0/29 closed as dup on 2020/08/05 10:53
linux-6.1 INFO: task hung in vcs_open 1 3 13d 63d 0/3 upstream: reported on 2026/09/01 17:44
upstream INFO: task hung in vcs_open (2) serial 1 1 2231d 2231d 0/29 auto-closed as invalid on 2020/12/23 12:34
upstream INFO: task hung in vcs_open (7) serial 1 1 961d 961d 0/29 auto-obsoleted due to no activity on 2024/06/15 13:53
linux-5.15 INFO: task hung in vcs_open 1 10 13h06m 92d 0/3 upstream: reported on 2026/08/03 15:31
linux-4.19 INFO: task hung in vcs_open 1 11 2187d 2500d 0/1 auto-closed as invalid on 2021/03/07 01:31
upstream INFO: task hung in vcs_open (10) prio:low kernel 1 83 70d 158d 0/29 auto-obsoleted due to no activity on 2026/11/03 16:58
upstream INFO: task hung in vcs_open (4) serial 1 2 1492d 1555d 0/29 auto-obsoleted due to no activity on 2023/01/02 16:56
linux-4.14 INFO: task hung in vcs_open 1 3 2345d 2429d 0/1 auto-closed as invalid on 2020/09/30 10:12
upstream INFO: task hung in vcs_open (6) serial 1 2 1111d 1175d 0/29 auto-obsoleted due to no activity on 2024/01/17 08:03
linux-4.19 INFO: task hung in vcs_open (2) 1 1 1470d 1470d 0/1 auto-obsoleted due to no activity on 2023/02/22 05:12
upstream INFO: task hung in vcs_open (8) nilfs serial 1 syz, C inconclusive 7 762d 768d 28/29 fixed on 2024/11/12 23:31

Sample crash report:
INFO: task syz.6.1173:11090 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.1173      state:D stack:27880 pid:11090 ppid:8644   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5393 [inline]
 __schedule+0x156f/0x4720 kernel/sched/core.c:6722
 schedule+0xbd/0x170 kernel/sched/core.c:6796
 schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
 ___down_common kernel/locking/semaphore.c:229 [inline]
 __down_common+0x31f/0x6b0 kernel/locking/semaphore.c:250
 down+0x80/0xd0 kernel/locking/semaphore.c:64
 console_lock+0x145/0x1b0 kernel/printk/printk.c:2686
 vcs_open+0x5d/0xc0 drivers/tty/vt/vc_screen.c:764
 chrdev_open+0x58c/0x600 fs/char_dev.c:414
 do_dentry_open+0x880/0x14b0 fs/open.c:929
 do_open fs/namei.c:3695 [inline]
 path_openat+0x284f/0x3270 fs/namei.c:3856
 do_filp_open+0x1f2/0x430 fs/namei.c:3883
 do_sys_openat2+0x134/0x1d0 fs/open.c:1422
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1448
 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: 0033:0x7f7f3799f559
RSP: 002b:00007f7f38897028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f7f37c26090 RCX: 00007f7f3799f559
RDX: 0000000000000842 RSI: 0000200000000480 RDI: ffffffffffffff9c
RBP: 00007f7f37a36b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7f37c26128 R14: 00007f7f37c26090 R15: 00007ffebd5db5d8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8e1322e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8e1322e0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8e1322e0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6669
3 locks held by kworker/0:2/56:
 #0: ffff888018c70d38 ((wq_completion)events#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff888018c70d38 ((wq_completion)events#2){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc9000131fd00 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc9000131fd00 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #2: ffff888022e78240 (&data->fib_lock){+.+.}-{3:3}, at: nsim_fib_event_work+0x285/0x32c0 drivers/net/netdevsim/fib.c:1491
2 locks held by getty/5545:
 #0: ffff88814c0440a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000327e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x43a/0x1400 drivers/tty/n_tty.c:2217
4 locks held by kworker/u4:12/7140:
3 locks held by kworker/u4:33/7166:
6 locks held by kworker/0:7/8454:
 #0: ffff88801be94938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff88801be94938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc900036efd00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc900036efd00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #2: ffff88814232b1d8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:1094 [inline]
 #2: ffff88814232b1d8 (&dev->mutex){....}-{3:3}, at: hub_event+0x188/0x4a80 drivers/usb/core/hub.c:5871
 #3: ffff8880315341d8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:1094 [inline]
 #3: ffff8880315341d8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x89/0x420 drivers/base/dd.c:1084
 #4: ffff8880269e11a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:1094 [inline]
 #4: ffff8880269e11a8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x89/0x420 drivers/base/dd.c:1084
 #5: ffffffff8dfdc9d0 (umhelper_sem){++++}-{3:3}, at: usermodehelper_read_trylock+0xfd/0x2b0 kernel/umh.c:215
2 locks held by syz.5.996/10475:
2 locks held by syz.2.1281/11469:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
 #1: ffff888076aea1c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_init_dev+0x74/0x4c0 drivers/tty/tty_io.c:1415
1 lock held by syz.9.1306/11537:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
1 lock held by syz.7.1320/11580:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
1 lock held by syz.1.1340/11722:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd0/0x2c0 drivers/tty/pty.c:823
1 lock held by syz.8.1356/11773:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
1 lock held by syz.0.1362/11815:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
4 locks held by udevd/12140:
 #0: ffff888063b2e9e0 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xa1/0xc50 fs/seq_file.c:182
 #1: ffff88808b130888 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x5d/0x410 fs/kernfs/file.c:172
 #2: ffff88808f1258c0 (kn->active#19){++++}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff88808f1258c0 (kn->active#19){++++}-{0:0}, at: kernfs_seq_start+0xb2/0x410 fs/kernfs/file.c:173
 #3: ffff8880315341d8 (&dev->mutex){....}-{3:3}, at: device_lock_interruptible include/linux/device.h:1099 [inline]
 #3: ffff8880315341d8 (&dev->mutex){....}-{3:3}, at: manufacturer_show+0x26/0xa0 drivers/usb/core/sysfs.c:142
1 lock held by syz.4.1391/12154:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
1 lock held by syz.6.1448/12414:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
1 lock held by syz.2.1479/12567:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
1 lock held by syz.3.1513/12756:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd0/0x2c0 drivers/tty/pty.c:823
1 lock held by syz.9.1544/13048:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
1 lock held by syz.5.1550/13106:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xd90 drivers/tty/tty_io.c:2129
1 lock held by syz.1.1554/13151:
 #0: ffffffff8e8abb28 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd0/0x2c0 drivers/tty/pty.c:823
2 locks held by rm/13207:

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

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 10/07/2026
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>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/31 05:39 linux-6.6.y b5a1dc3ad482 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in vcs_open
* Struck through repros no longer work on HEAD.