syzbot


INFO: task hung in tty_ldisc_hangup

Status: upstream: reported on 2024/12/11 23:43
Reported-by: syzbot+625ae46624e60e563505@syzkaller.appspotmail.com
First crash: 10d, last: 10d
Similar bugs (7)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 INFO: task hung in tty_ldisc_hangup (2) C error 1 1179d 1329d 0/1 upstream: reported C repro on 2021/05/02 05:40
upstream INFO: task hung in tty_ldisc_hangup (2) serial 1 1116d 1116d 0/28 closed as invalid on 2022/02/07 19:09
linux-4.14 INFO: task hung in tty_ldisc_hangup (2) 1 1378d 1378d 0/1 auto-closed as invalid on 2021/07/12 09:20
linux-4.19 INFO: task hung in tty_ldisc_hangup C done 10 1773d 1840d 1/1 fixed on 2020/03/16 09:27
upstream INFO: task hung in tty_ldisc_hangup (3) serial 1 152d 152d 0/28 auto-obsoleted due to no activity on 2024/10/20 03:25
upstream INFO: task hung in tty_ldisc_hangup C inconclusive done 15 1766d 1841d 0/28 closed as dup on 2020/07/30 01:09
linux-4.14 INFO: task hung in tty_ldisc_hangup C done 17 1769d 1840d 1/1 fixed on 2020/03/18 22:57

Sample crash report:
INFO: task syz.8.1308:10514 blocked for more than 146 seconds.
      Not tainted 6.1.119-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.8.1308      state:D stack:28552 pid:10514 ppid:9901   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5241 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6558
 schedule+0xbf/0x180 kernel/sched/core.c:6634
 schedule_timeout+0xac/0x300 kernel/time/timer.c:1941
 down_write_failed drivers/tty/tty_ldsem.c:262 [inline]
 __ldsem_down_write_nested+0x3ae/0x910 drivers/tty/tty_ldsem.c:324
 __tty_ldisc_lock drivers/tty/tty_ldisc.c:290 [inline]
 tty_ldisc_lock+0x68/0xb0 drivers/tty/tty_ldisc.c:314
 tty_ldisc_hangup+0x223/0x4b0 drivers/tty/tty_ldisc.c:719
 __tty_hangup+0x3e4/0x620 drivers/tty/tty_io.c:631
 tty_vhangup drivers/tty/tty_io.c:701 [inline]
 tty_ioctl+0x591/0xbd0 drivers/tty/tty_io.c:2716
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f594497ff19
RSP: 002b:00007f59447bd058 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5944b46160 RCX: 00007f594497ff19
RDX: 0000000000000000 RSI: 0000000000005437 RDI: 0000000000000003
RBP: 00007f59449f3cc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f5944b46160 R15: 00007ffcd9f2e298
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8d32b110 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xe30 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffffffff8d32b910 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xe30 kernel/rcu/tasks.h:517
2 locks held by kworker/1:0/22:
 #0: ffff888017c72138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
 #1: ffffc900001c7d20 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
1 lock held by khungtaskd/27:
 #0: ffffffff8d32af40 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8d32af40 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8d32af40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6510
2 locks held by dhcpcd/3915:
 #0: ffffffff8e4f0ce8 (vlan_ioctl_mutex){+.+.}-{3:3}, at: sock_ioctl+0x521/0x770 net/socket.c:1283
 #1: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: vlan_ioctl_handler+0x114/0x980 net/8021q/vlan.c:553
2 locks held by getty/4003:
 #0: ffff88814cf2e098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
 #1: ffffc9000325e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6a7/0x1db0 drivers/tty/n_tty.c:2198
3 locks held by kworker/u4:5/4302:
 #0: ffff888017c79138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
 #1: ffffc900046c7d20 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
 #2: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xa/0x50 net/core/link_watch.c:263
3 locks held by kworker/u4:7/4328:
4 locks held by kworker/u4:9/4348:
 #0: ffff888017e16938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
 #1: ffffc90004887d20 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
 #2: ffffffff8e4fe3d0 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0xf1/0xb60 net/core/net_namespace.c:566
 #3: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: vti6_exit_batch_net+0xb0/0x410 net/ipv6/ip6_vti.c:1185
2 locks held by kworker/u4:14/4408:
1 lock held by syz.5.1303/10435:
2 locks held by syz.9.1305/10473:
2 locks held by syz.0.1297/10496:
2 locks held by syz.8.1308/10514:
 #0: ffff88807f1bb1c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: __tty_hangup+0xc0/0x620 drivers/tty/tty_io.c:591
 #1: ffff88807f1bb098 (&tty->ldisc_sem){++++}-{0:0}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:290 [inline]
 #1: ffff88807f1bb098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock+0x68/0xb0 drivers/tty/tty_ldisc.c:314
2 locks held by syz-executor/10760:
 #0: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7c1/0xff0 net/core/rtnetlink.c:6147
 #1: ffffffff8d330538 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:323 [inline]
 #1: ffffffff8d330538 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x360/0x930 kernel/rcu/tree_exp.h:962
1 lock held by syz-executor/10763:
 #0: ffffffff8d330538 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
 #0: ffffffff8d330538 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x4f0/0x930 kernel/rcu/tree_exp.h:962
1 lock held by syz-executor/10768:
 #0: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7c1/0xff0 net/core/rtnetlink.c:6147
1 lock held by syz-executor/10781:
 #0: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
 #0: ffffffff8e50a768 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x7c1/0xff0 net/core/rtnetlink.c:6147

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted 6.1.119-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 nmi_cpu_backtrace+0x4e1/0x560 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x1ae/0x3f0 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+0xf88/0xfd0 kernel/hung_task.c:377
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 10435 Comm: syz.5.1303 Not tainted 6.1.119-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:arch_atomic_long_read include/linux/atomic/atomic-long.h:29 [inline]
RIP: 0010:atomic_long_read include/linux/atomic/atomic-instrumented.h:1266 [inline]
RIP: 0010:__mutex_trylock_common+0xa7/0x2e0 kernel/locking/mutex.c:107
Code: 7e 48 89 44 24 18 be 08 00 00 00 e8 43 53 78 00 4c 89 e0 48 c1 e8 03 42 80 3c 30 00 74 08 4c 89 e7 e8 9d 51 78 00 49 8b 1c 24 <4d> 89 fd 49 c1 ed 03 48 c7 c0 60 31 35 97 48 c1 e8 03 48 89 44 24
RSP: 0018:ffffc900037bf9a0 EFLAGS: 00000246
RAX: 1ffff1100fe37619 RBX: ffff88802faf8000 RCX: ffffffff8169d35d
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88807f1bb0c8
RBP: ffffc900037bfa70 R08: dffffc0000000000 R09: ffffed100fe3761a
R10: 0000000000000000 R11: dffffc0000000001 R12: ffff88807f1bb0c8
R13: ffff88807f1bb0c8 R14: dffffc0000000000 R15: ffffc900037bfa00
FS:  00007f48f1cd46c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000564e5a9d3250 CR3: 000000005f2c3000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 __mutex_trylock kernel/locking/mutex.c:152 [inline]
 __mutex_lock_common kernel/locking/mutex.c:606 [inline]
 __mutex_lock+0x14d/0xd80 kernel/locking/mutex.c:747
 tty_write_lock+0x58/0x90 drivers/tty/tty_io.c:947
 set_termios+0x472/0x6b0 drivers/tty/tty_ioctl.c:509
 tty_mode_ioctl+0x4f6/0x690
 tty_ioctl+0x88e/0xbd0 drivers/tty/tty_io.c:2785
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f48f0f7ff19
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f48f1cd4058 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f48f1145fa0 RCX: 00007f48f0f7ff19
RDX: 0000000020000000 RSI: 0000000000005404 RDI: 0000000000000009
RBP: 00007f48f0ff3cc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f48f1145fa0 R15: 00007ffffb9ef578
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/12/11 23:42 linux-6.1.y e4d90d63d385 ff949d25 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: task hung in tty_ldisc_hangup
* Struck through repros no longer work on HEAD.