INFO: task hung in release_tty

Status: auto-closed as invalid on 2020/11/12 17:59
Reported-by: syzbot+6ff5629f3ac522892112@syzkaller.appspotmail.com
First crash: 2417d, last: 2218d
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in release_tty (2) serial 1 2 1738d 1816d 0/29 auto-closed as invalid on 2022/02/05 17:28
linux-4.19 INFO: task hung in release_tty 1 2 2213d 2285d 0/1 auto-closed as invalid on 2020/11/18 01:32
upstream INFO: task hung in release_tty (4) kernel 1 2 470d 536d 0/29 auto-obsoleted due to no activity on 2025/07/28 01:59
upstream INFO: task hung in release_tty (3) serial 1 3 641d 707d 0/29 auto-obsoleted due to no activity on 2025/02/07 03:06
upstream INFO: task hung in release_tty serial 1 3 2353d 2408d 0/29 auto-closed as invalid on 2020/06/30 16:07
linux-5.15 INFO: task hung in release_tty 1 1 12d 12d 0/3 upstream: reported on 2026/07/30 19:13

Sample crash report:
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
INFO: task syz-executor.0:19826 blocked for more than 140 seconds.
      Not tainted 4.14.184-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D28576 19826   6356 0x80000002
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x8a6/0x1d70 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x86c/0xe50 kernel/time/timer.c:1723
 __down_common kernel/locking/semaphore.c:221 [inline]
 __down+0x17f/0x280 kernel/locking/semaphore.c:238
 down+0x57/0x80 kernel/locking/semaphore.c:62
 console_lock+0x24/0x70 kernel/printk/printk.c:2216
 con_shutdown+0x3d/0x90 drivers/tty/vt/vt.c:2941
 release_tty+0xba/0x750 drivers/tty/tty_io.c:1501
 tty_release_struct+0x37/0x50 drivers/tty/tty_io.c:1616
 tty_release+0xaa8/0xd60 drivers/tty/tty_io.c:1776
 __fput+0x25f/0x7a0 fs/file_table.c:210
 task_work_run+0x113/0x190 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x9fb/0x2ae0 kernel/exit.c:858
 do_group_exit+0x100/0x2e0 kernel/exit.c:955
 get_signal+0x385/0x1c90 kernel/signal.c:2423
 do_signal+0x7c/0x15d0 arch/x86/kernel/signal.c:814
 exit_to_usermode_loop+0x160/0x200 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45cba9
RSP: 002b:00007fbef71f5cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000078c0e8 RCX: 000000000045cba9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000078c0e8
RBP: 000000000078c0e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078c0ec
R13: 00007ffc91ca9c5f R14: 00007fbef71f69c0 R15: 000000000078c0ec
INFO: task syz-executor.0:20629 blocked for more than 140 seconds.
      Not tainted 4.14.184-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D29472 20629   6356 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x8a6/0x1d70 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3486
 __mutex_lock_common kernel/locking/mutex.c:833 [inline]
 __mutex_lock+0x5f0/0x1430 kernel/locking/mutex.c:893
 fb_open+0xb7/0x400 drivers/video/fbdev/core/fbmem.c:1468
 chrdev_open+0x1fc/0x540 fs/char_dev.c:423
 do_dentry_open+0x44b/0xec0 fs/open.c:777
 vfs_open+0x105/0x220 fs/open.c:888
 do_last fs/namei.c:3428 [inline]
 path_openat+0xb68/0x2aa0 fs/namei.c:3569
 do_filp_open+0x18e/0x250 fs/namei.c:3603
 do_sys_open+0x292/0x3e0 fs/open.c:1081
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45cba9
RSP: 002b:00007fbef7216c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f9ea0 RCX: 000000000045cba9
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007f6 R14: 00000000004cad3c R15: 00007fbef72176d4

Showing all locks held in the system:
1 lock held by khungtaskd/1055:
 #0:  (tasklist_lock){.+.?}, at: [<ffffffff8146c8d0>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
1 lock held by in:imklog/6038:
 #0:  (&f->f_pos_lock){+.+.}, at: [<ffffffff8191e4e6>] __fdget_pos+0xa6/0xc0 fs/file.c:769
2 locks held by agetty/6055:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833bd922>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff833b8f04>] n_tty_read+0x1e4/0x16e0 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.0/19826:
 #0:  (tty_mutex){+.+.}, at: [<ffffffff833a529c>] tty_release_struct+0x2c/0x50 drivers/tty/tty_io.c:1615
1 lock held by syz-executor.0/20629:
 #0:  (&fb_info->lock){+.+.}, at: [<ffffffff83182237>] fb_open+0xb7/0x400 drivers/video/fbdev/core/fbmem.c:1468

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

NMI backtrace for cpu 1
CPU: 1 PID: 1055 Comm: khungtaskd Not tainted 4.14.184-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x13a/0x17f lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
 watchdog+0x5e2/0xb80 kernel/hung_task.c:274
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 20591 Comm: syz-executor.0 Not tainted 4.14.184-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88808851c000 task.stack: ffff888058b28000
RIP: 0010:__sanitizer_cov_trace_pc+0x41/0x50 kernel/kcov.c:88
RSP: 0018:ffff888058b2f3d8 EFLAGS: 00000216
RAX: 0000000000040000 RBX: ffff8880000a0050 RCX: ffffc90007893000
RDX: 0000000000040000 RSI: ffffffff831f9ef3 RDI: ffff888058b2f490
RBP: 0000000000000050 R08: 000000000000ffff R09: ffffed10432389b4
R10: ffffed10432389b3 R11: ffff8882191c4d9f R12: ffff8880000a0034
R13: 0000000000000000 R14: 00000000de28bbae R15: 000000000000004f
FS:  00007fbef7259700(0000) GS:ffff8880aec00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c00049da6c CR3: 0000000090722000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 writeb arch/x86/include/asm/io.h:65 [inline]
 vga16fb_fillrect+0x943/0x1880 drivers/video/fbdev/vga16fb.c:923
 bit_clear_margins+0x2a4/0x480 drivers/video/fbdev/core/bitblit.c:232
 fbcon_clear_margins+0x274/0x300 drivers/video/fbdev/core/fbcon.c:1320
 fbcon_switch+0xc4e/0x1700 drivers/video/fbdev/core/fbcon.c:2302
 redraw_screen+0x332/0x760 drivers/tty/vt/vt.c:689
 fbcon_modechanged+0x552/0x800 drivers/video/fbdev/core/fbcon.c:2949
 fbcon_event_notify+0x11a/0x1750 drivers/video/fbdev/core/fbcon.c:3302
 notifier_call_chain+0x107/0x1a0 kernel/notifier.c:93
 __blocking_notifier_call_chain kernel/notifier.c:317 [inline]
 __blocking_notifier_call_chain kernel/notifier.c:304 [inline]
 blocking_notifier_call_chain kernel/notifier.c:328 [inline]
 blocking_notifier_call_chain+0x79/0x90 kernel/notifier.c:325
 fb_set_var+0xaad/0xc70 drivers/video/fbdev/core/fbmem.c:1054
 do_fb_ioctl+0x3cc/0x840 drivers/video/fbdev/core/fbmem.c:1127
 fb_ioctl+0xda/0x120 drivers/video/fbdev/core/fbmem.c:1242
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xfe0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45cba9
RSP: 002b:00007fbef7258c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004e6560 RCX: 000000000045cba9
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000004
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000311 R14: 00000000004c59ee R15: 00007fbef72596d4
Code: e2 00 01 1f 00 75 0b 8b 90 58 13 00 00 83 fa 01 74 01 c3 48 8b 34 24 48 8b 88 60 13 00 00 8b 80 5c 13 00 00 48 8b 11 48 83 c2 01 <48> 39 d0 76 e2 48 89 34 d1 48 89 11 c3 66 90 41 54 49 89 fc 48

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/07/15 17:59 linux-4.14.y b850307b279c ada108d0 .config console log report ci2-linux-4-14
2020/07/03 09:04 linux-4.14.y b850307b279c f30c14bf .config console log report ci2-linux-4-14
2020/07/03 07:08 linux-4.14.y b850307b279c f30c14bf .config console log report ci2-linux-4-14
2020/06/30 02:08 linux-4.14.y b850307b279c 917afeaa .config console log report ci2-linux-4-14
2020/04/16 20:32 linux-4.14.y c10b57a567e4 c743fcb3 .config console log report ci2-linux-4-14
2019/12/29 19:56 linux-4.14.y e1f7d50ae3a3 af6b8ef8 .config console log report ci2-linux-4-14
* Struck through repros no longer work on HEAD.