syzbot


INFO: task hung in commit_echoes

Status: auto-closed as invalid on 2020/04/28 11:37
Reported-by: syzbot+aa345f2d1fc58d8f0255@syzkaller.appspotmail.com
First crash: 952d, last: 952d
similar bugs (3):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in commit_echoes 1 1499d 1495d 9/23 fixed on 2018/07/09 18:05
android-49 INFO: task hung in commit_echoes C 44 1492d 1215d 0/3 public: reported C repro on 2019/04/11 08:44
upstream INFO: task hung in commit_echoes (2) 3 683d 720d 0/23 auto-closed as invalid on 2020/12/23 20:14

Sample crash report:
kobject: 'bridge0' (000000005396136e): calling ktype release
kobject: 'bridge0': free name
kobject: 'lo' (00000000676eaa9d): kobject_cleanup, parent           (null)
kobject: 'lo' (00000000676eaa9d): calling ktype release
kobject: 'lo': free name
INFO: task kworker/u4:7:9088 blocked for more than 140 seconds.
      Not tainted 4.19.91-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:7    D25640  9088      2 0x80000000
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 context_switch kernel/sched/core.c:2826 [inline]
 __schedule+0x866/0x1dc0 kernel/sched/core.c:3515
 schedule+0x92/0x1c0 kernel/sched/core.c:3559
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3617
 __mutex_lock_common kernel/locking/mutex.c:1002 [inline]
 __mutex_lock+0x726/0x1300 kernel/locking/mutex.c:1072
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
 commit_echoes+0x53/0x1c0 drivers/tty/n_tty.c:776
 n_tty_receive_char_fast drivers/tty/n_tty.c:1447 [inline]
 n_tty_receive_buf_fast drivers/tty/n_tty.c:1607 [inline]
 __receive_buf drivers/tty/n_tty.c:1642 [inline]
 n_tty_receive_buf_common+0x1e23/0x2ab0 drivers/tty/n_tty.c:1740
 n_tty_receive_buf2+0x34/0x40 drivers/tty/n_tty.c:1775
 tty_ldisc_receive_buf+0xad/0x1c0 drivers/tty/tty_buffer.c:456
 tty_port_default_receive_buf+0x7d/0xb0 drivers/tty/tty_port.c:38
 receive_buf drivers/tty/tty_buffer.c:476 [inline]
 flush_to_ldisc+0x222/0x390 drivers/tty/tty_buffer.c:528
 process_one_work+0x989/0x1750 kernel/workqueue.c:2153
 worker_thread+0x98/0xe40 kernel/workqueue.c:2296
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Showing all locks held in the system:
1 lock held by khungtaskd/1068:
 #0: 000000000f0868dc (rcu_read_lock){....}, at: debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4438
1 lock held by rsyslogd/7580:
 #0: 000000007df913e3 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110 fs/file.c:767
2 locks held by getty/7703:
 #0: 0000000040832f46 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 000000001a23f276 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7704:
 #0: 00000000b97455b1 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000bb957077 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7705:
 #0: 0000000004a9015d (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000d6381f73 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7706:
 #0: 00000000264fd78c (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 000000005dc83e9b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7707:
 #0: 00000000416fef6e (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000d6200ead (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7708:
 #0: 000000008f91ba1c (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 00000000cb3e789f (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/7709:
 #0: 0000000049abf609 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
 #1: 000000008eec52b0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
6 locks held by kworker/u4:7/9088:
 #0: 0000000082eba9f3 ((wq_completion)"events_unbound"){+.+.}, at: __write_once_size include/linux/compiler.h:220 [inline]
 #0: 0000000082eba9f3 ((wq_completion)"events_unbound"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: 0000000082eba9f3 ((wq_completion)"events_unbound"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
 #0: 0000000082eba9f3 ((wq_completion)"events_unbound"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline]
 #0: 0000000082eba9f3 ((wq_completion)"events_unbound"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
 #0: 0000000082eba9f3 ((wq_completion)"events_unbound"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0: 0000000082eba9f3 ((wq_completion)"events_unbound"){+.+.}, at: process_one_work+0x87e/0x1750 kernel/workqueue.c:2124
 #1: 00000000e2da741b ((work_completion)(&buf->work)){+.+.}, at: process_one_work+0x8b4/0x1750 kernel/workqueue.c:2128
 #2: 000000008fa238bc (&buf->lock){+.+.}, at: flush_to_ldisc+0x3d/0x390 drivers/tty/tty_buffer.c:500
 #3: 0000000040832f46 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x22/0x90 drivers/tty/tty_ldisc.c:293
 #4: 000000002aa93cc7 (&tty->termios_rwsem){++++}, at: n_tty_receive_buf_common+0x8a/0x2ab0 drivers/tty/n_tty.c:1703
 #5: 000000002a056105 (&ldata->output_lock){+.+.}, at: commit_echoes+0x53/0x1c0 drivers/tty/n_tty.c:776
5 locks held by syz-executor.0/837:

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

NMI backtrace for cpu 0
CPU: 0 PID: 1068 Comm: khungtaskd Not tainted 4.19.91-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+0x197/0x210 lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
 watchdog+0x9df/0xee0 kernel/hung_task.c:287
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 837 Comm: syz-executor.0 Not tainted 4.19.91-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:94
Code: 41 bc f4 ff ff ff e8 83 64 ea ff 48 c7 05 54 29 5e 09 00 00 00 00 e9 96 e9 ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <55> 48 89 e5 48 8b 75 08 65 48 8b 04 25 40 ee 01 00 65 8b 15 78 a9
RSP: 0018:ffff888093a37380 EFLAGS: 00000282
RAX: 0000000000000280 RBX: 0000000000000000 RCX: ffffffff8383a1fd
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000005
RBP: ffff888093a373c8 R08: ffff8880434fc4c0 R09: 0000000000000040
R10: ffffed1014b7a01b R11: ffff8880a5bd00df R12: 0000000000000000
R13: 0000000000000000 R14: ffff8880000a0280 R15: ffff8880000a0280
FS:  00007fd7ef51e700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c4248bd120 CR3: 000000004b3c4000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 cfb_fillrect+0x423/0x7c0 drivers/video/fbdev/core/cfbfillrect.c:327
 vga16fb_fillrect+0x6ce/0x19b0 drivers/video/fbdev/vga16fb.c:951
 bit_clear_margins+0x30b/0x530 drivers/video/fbdev/core/bitblit.c:232
 fbcon_clear_margins+0x2e3/0x370 drivers/video/fbdev/core/fbcon.c:1339
 ypan_up_redraw drivers/video/fbdev/core/fbcon.c:1524 [inline]
 fbcon_scroll+0x141c/0x3780 drivers/video/fbdev/core/fbcon.c:1902
 con_scroll+0x5b4/0x6b0 drivers/tty/vt/vt.c:631
 lf+0x285/0x2e0 drivers/tty/vt/vt.c:1454
 do_con_trol+0x605/0x6070 drivers/tty/vt/vt.c:2122
 do_con_write.part.0+0xfd5/0x1eb0 drivers/tty/vt/vt.c:2773
 do_con_write drivers/tty/vt/vt.c:2541 [inline]
 con_write+0x46/0xd0 drivers/tty/vt/vt.c:3110
 process_output_block drivers/tty/n_tty.c:593 [inline]
 n_tty_write+0x3f9/0x1140 drivers/tty/n_tty.c:2331
 do_tty_write drivers/tty/tty_io.c:960 [inline]
 tty_write+0x458/0x7a0 drivers/tty/tty_io.c:1044
 __vfs_write+0x114/0x810 fs/read_write.c:485
 vfs_write+0x20c/0x560 fs/read_write.c:549
 ksys_write+0x14f/0x2d0 fs/read_write.c:599
 __do_sys_write fs/read_write.c:611 [inline]
 __se_sys_write fs/read_write.c:608 [inline]
 __x64_sys_write+0x73/0xb0 fs/read_write.c:608
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a919
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd7ef51dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a919
RDX: 00000000000002c1 RSI: 0000000020000880 RDI: 0000000000000005
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd7ef51e6d4
R13: 00000000004cbd7a R14: 00000000004e5b48 R15: 00000000ffffffff

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-19 2019/12/30 11:37 linux-4.19.y 672481c2deff af6b8ef8 .config log report