syzbot


INFO: task hung in flush_to_ldisc (3)

Status: auto-closed as invalid on 2021/08/25 00:39
Reported-by: syzbot+a92cf3dde205af194b86@syzkaller.appspotmail.com
First crash: 525d, last: 525d
similar bugs (8):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 INFO: task hung in flush_to_ldisc (2) 1 811d 811d 0/1 auto-closed as invalid on 2020/11/11 17:44
upstream INFO: task hung in flush_to_ldisc (2) 1 541d 541d 0/24 auto-closed as invalid on 2021/06/09 11:04
linux-4.19 INFO: task hung in flush_to_ldisc 10 960d 1023d 0/1 auto-closed as invalid on 2020/06/15 14:09
upstream INFO: task hung in flush_to_ldisc C inconclusive done 15 963d 1033d 17/24 fixed on 2020/11/16 12:12
linux-4.14 INFO: task hung in flush_to_ldisc (3) 1 573d 573d 0/1 auto-closed as invalid on 2021/07/07 16:40
upstream INFO: task hung in flush_to_ldisc (3) C inconclusive 3 242d 431d 0/24 closed as invalid on 2022/02/08 10:26
linux-4.14 INFO: task hung in flush_to_ldisc (2) 1 764d 764d 0/1 auto-closed as invalid on 2020/12/28 13:53
linux-4.14 INFO: task hung in flush_to_ldisc 8 952d 1023d 0/1 auto-closed as invalid on 2020/06/23 11:01

Sample crash report:
Bluetooth: hci4: command 0x0406 tx timeout
ieee802154 phy0 wpan0: encryption failed: -22
ieee802154 phy1 wpan1: encryption failed: -22
ieee802154 phy0 wpan0: encryption failed: -22
ieee802154 phy1 wpan1: encryption failed: -22
INFO: task kworker/u4:0:7 blocked for more than 140 seconds.
      Not tainted 4.19.188-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:0    D27168     7      2 0x80000000
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x887/0x2040 kernel/sched/core.c:3517
 schedule+0x8d/0x1b0 kernel/sched/core.c:3561
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3619
 __mutex_lock_common kernel/locking/mutex.c:1005 [inline]
 __mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1075
 flush_to_ldisc+0x3e/0x390 drivers/tty/tty_buffer.c:500
 process_one_work+0x864/0x1570 kernel/workqueue.c:2152
 worker_thread+0x64c/0x1130 kernel/workqueue.c:2295
 kthread+0x33f/0x460 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
INFO: task syz-executor.2:17234 blocked for more than 140 seconds.
      Not tainted 4.19.188-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D29240 17234   8144 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x887/0x2040 kernel/sched/core.c:3517
 schedule+0x8d/0x1b0 kernel/sched/core.c:3561
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3619
 __mutex_lock_common kernel/locking/mutex.c:1005 [inline]
 __mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1075
 paste_selection+0x125/0x470 drivers/tty/vt/selection.c:372
 tioclinux+0x122/0x510 drivers/tty/vt/vt.c:3054
 vt_ioctl+0x163e/0x2380 drivers/tty/vt/vt_ioctl.c:372
 tty_ioctl+0x5b0/0x15c0 drivers/tty/tty_io.c:2669
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665f9
Code: Bad RIP value.
RSP: 002b:00007fd2d3d6e188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665f9
RDX: 0000000020000040 RSI: 000000000000541c RDI: 0000000000000003
RBP: 00000000004bfce1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007fff664b94ef R14: 00007fd2d3d6e300 R15: 0000000000022000
INFO: task syz-executor.2:17237 blocked for more than 140 seconds.
      Not tainted 4.19.188-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D29240 17237   8144 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x887/0x2040 kernel/sched/core.c:3517
 schedule+0x8d/0x1b0 kernel/sched/core.c:3561
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3619
 __mutex_lock_common kernel/locking/mutex.c:1005 [inline]
 __mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1075
 paste_selection+0x125/0x470 drivers/tty/vt/selection.c:372
 tioclinux+0x122/0x510 drivers/tty/vt/vt.c:3054
 vt_ioctl+0x163e/0x2380 drivers/tty/vt/vt_ioctl.c:372
 tty_ioctl+0x5b0/0x15c0 drivers/tty/tty_io.c:2669
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665f9
Code: Bad RIP value.
RSP: 002b:00007fd2d3d4d188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056c008 RCX: 00000000004665f9
RDX: 0000000020000040 RSI: 000000000000541c RDI: 0000000000000003
RBP: 00000000004bfce1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008
R13: 00007fff664b94ef R14: 00007fd2d3d4d300 R15: 0000000000022000

Showing all locks held in the system:
3 locks held by kworker/u4:0/7:
 #0: 0000000021a1cc83 ((wq_completion)"events_unbound"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2123
 #1: 000000009d0a59f3 ((work_completion)(&buf->work)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2127
 #2: 0000000057f781ba (&buf->lock){+.+.}, at: flush_to_ldisc+0x3e/0x390 drivers/tty/tty_buffer.c:500
1 lock held by khungtaskd/1569:
 #0: 0000000074dd28c1 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440
2 locks held by agetty/7855:
 #0: 000000005432b280 (&tty->legacy_mutex){+.+.}, at: tty_lock+0x6a/0xa0 drivers/tty/tty_mutex.c:19
 #1: 00000000188d157d (&tty->ldisc_sem){++++}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:320 [inline]
 #1: 00000000188d157d (&tty->ldisc_sem){++++}, at: tty_ldisc_lock+0x4d/0x90 drivers/tty/tty_ldisc.c:344
2 locks held by syz-executor.4/17179:
 #0: 00000000188d157d (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #1: 0000000057f781ba (&buf->lock){+.+.}, at: paste_selection+0x125/0x470 drivers/tty/vt/selection.c:372
2 locks held by syz-executor.2/17234:
 #0: 00000000188d157d (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #1: 0000000057f781ba (&buf->lock){+.+.}, at: paste_selection+0x125/0x470 drivers/tty/vt/selection.c:372
2 locks held by syz-executor.2/17237:
 #0: 00000000188d157d (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #1: 0000000057f781ba (&buf->lock){+.+.}, at: paste_selection+0x125/0x470 drivers/tty/vt/selection.c:372

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

NMI backtrace for cpu 1
CPU: 1 PID: 1569 Comm: khungtaskd Not tainted 4.19.188-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1a6/0x1f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
 watchdog+0x991/0xe60 kernel/hung_task.c:287
 kthread+0x33f/0x460 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4682 Comm: systemd-journal Not tainted 4.19.188-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:free_uid+0x0/0x230 kernel/user.c:166
Code: 5d 41 5c 41 5d c3 e8 6f a8 5d 00 e9 75 ff ff ff e8 f5 a8 5d 00 eb 9b e8 1e 2f fd ff 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 <41> 56 41 55 49 bd 00 00 00 00 00 fc ff df 41 54 55 48 89 fd 53 48
RSP: 0018:ffff8880a154fe18 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: ffff8880b2a212a8 RCX: ffffffff813fe8cf
RDX: 1ffff11016544252 RSI: ffffffff813fe8dd RDI: ffffffff89f50220
RBP: ffff8880b2a21200 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff89f5aa00
R13: ffff8880b2a212a0 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f7317c9b8c0(0000) GS:ffff8880ba000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f73150e0000 CR3: 00000000a1a74000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 put_cred_rcu+0x245/0x4a0 kernel/cred.c:124
 __put_cred+0x1de/0x250 kernel/cred.c:151
 put_cred include/linux/cred.h:276 [inline]
 do_faccessat+0x64e/0x7a0 fs/open.c:438
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f7316f569c7
Code: 83 c4 08 48 3d 01 f0 ff ff 73 01 c3 48 8b 0d c8 d4 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 15 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 d4 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffd2ccbe278 EFLAGS: 00000246 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 00007ffd2ccc1190 RCX: 00007f7316f569c7
RDX: 00007f73179c7a00 RSI: 0000000000000000 RDI: 000056262f5de9a3
RBP: 00007ffd2ccbe2b0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000069 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffd2ccc1190 R15: 00007ffd2ccbe7a0

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-19 2021/04/27 00:38 linux-4.19.y 2965db2e004c 8ee2dea6 .config log report info INFO: task hung in flush_to_ldisc
* Struck through repros no longer work on HEAD.