syzbot


INFO: task hung in con_write

Status: auto-closed as invalid on 2020/09/14 21:41
Reported-by: syzbot+b636ed4d5da16446df4f@syzkaller.appspotmail.com
First crash: 768d, last: 768d
similar bugs (3):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in con_write (2) 3 709d 757d 0/22 auto-closed as invalid on 2020/10/13 06:51
linux-4.19 INFO: task hung in con_write 2 737d 804d 0/1 auto-closed as invalid on 2020/10/15 09:20
upstream INFO: task hung in con_write 1 922d 922d 0/22 auto-closed as invalid on 2020/03/14 17:26

Sample crash report:
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
INFO: task syz-executor.5:19182 blocked for more than 140 seconds.
      Not tainted 4.14.180-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D28528 19182   6355 0x00000004
Call Trace:
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x946/0xe40 kernel/time/timer.c:1723
 __down_common kernel/locking/semaphore.c:221 [inline]
 __down+0x160/0x290 kernel/locking/semaphore.c:238
 down+0x57/0x80 kernel/locking/semaphore.c:62
 console_lock+0x24/0x70 kernel/printk/printk.c:2216
 con_flush_chars drivers/tty/vt/vt.c:2875 [inline]
 con_flush_chars drivers/tty/vt/vt.c:2867 [inline]
 con_write+0x60/0xc0 drivers/tty/vt/vt.c:2799
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x375/0xe30 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:959 [inline]
 tty_write+0x3f0/0x700 drivers/tty/tty_io.c:1043
 do_loop_readv_writev fs/read_write.c:698 [inline]
 do_loop_readv_writev fs/read_write.c:682 [inline]
 do_iter_write fs/read_write.c:956 [inline]
 do_iter_write+0x3d9/0x550 fs/read_write.c:935
 vfs_writev+0x170/0x2a0 fs/read_write.c:999
 do_writev+0xfc/0x2c0 fs/read_write.c:1034
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45ca29
RSP: 002b:00007f570bccfc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 000000000050d640 RCX: 000000000045ca29
RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000004
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000d20 R14: 00000000004cb469 R15: 00007f570bcd06d4
INFO: task syz-executor.5:19221 blocked for more than 140 seconds.
      Not tainted 4.14.180-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D29616 19221   6355 0x00000004
Call Trace:
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x946/0xe40 kernel/time/timer.c:1723
 __down_common kernel/locking/semaphore.c:221 [inline]
 __down+0x160/0x290 kernel/locking/semaphore.c:238
 down+0x57/0x80 kernel/locking/semaphore.c:62
 console_lock+0x24/0x70 kernel/printk/printk.c:2216
 vcs_open+0x3d/0x80 drivers/tty/vt/vc_screen.c:599
 chrdev_open+0x1fc/0x540 fs/char_dev.c:423
 do_dentry_open+0x732/0xe90 fs/open.c:777
 vfs_open+0x105/0x220 fs/open.c:888
 do_last fs/namei.c:3428 [inline]
 path_openat+0x8ca/0x3c50 fs/namei.c:3569
 do_filp_open+0x18e/0x250 fs/namei.c:3603
 do_sys_open+0x29d/0x3f0 fs/open.c:1081
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45ca29
RSP: 002b:00007f570bc6cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f9080 RCX: 000000000045ca29
RDX: 0000000000103c00 RSI: 0000000020000240 RDI: ffffffffffffff9c
RBP: 000000000078c0e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000809 R14: 00000000004cae4e R15: 00007f570bc6d6d4
INFO: task syz-executor.4:19223 blocked for more than 140 seconds.
      Not tainted 4.14.180-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D29424 19223   6358 0x00000004
Call Trace:
 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+0x73c/0x1470 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+0x732/0xe90 fs/open.c:777
 vfs_open+0x105/0x220 fs/open.c:888
 do_last fs/namei.c:3428 [inline]
 path_openat+0x8ca/0x3c50 fs/namei.c:3569
 do_filp_open+0x18e/0x250 fs/namei.c:3603
 do_sys_open+0x29d/0x3f0 fs/open.c:1081
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45ca29
RSP: 002b:00007fa68d6b6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f7640 RCX: 000000000045ca29
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007a0 R14: 00000000004ca744 R15: 00007fa68d6b76d4

Showing all locks held in the system:
1 lock held by khungtaskd/1056:
 #0:  (tasklist_lock){.+.?}, at: [<ffffffff81465d33>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
1 lock held by in:imklog/6033:
 #0:  (&f->f_pos_lock){+.+.}, at: [<ffffffff8191bb06>] __fdget_pos+0xa6/0xc0 fs/file.c:769
4 locks held by syz-executor.5/19182:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833b1c62>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&tty->atomic_write_lock){+.+.}, at: [<ffffffff833977cd>] tty_write_lock+0x1d/0x60 drivers/tty/tty_io.c:885
 #2:  (&tty->termios_rwsem){++++}, at: [<ffffffff833a43e7>] n_tty_write+0x187/0xe30 drivers/tty/n_tty.c:2316
 #3:  (&ldata->output_lock){+.+.}, at: [<ffffffff833a46c4>] process_output_block drivers/tty/n_tty.c:550 [inline]
 #3:  (&ldata->output_lock){+.+.}, at: [<ffffffff833a46c4>] n_tty_write+0x464/0xe30 drivers/tty/n_tty.c:2333
1 lock held by syz-executor.4/19223:
 #0:  (&fb_info->lock){+.+.}, at: [<ffffffff83174827>] fb_open+0xb7/0x400 drivers/video/fbdev/core/fbmem.c:1468

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

NMI backtrace for cpu 0
CPU: 0 PID: 1056 Comm: khungtaskd Not tainted 4.14.180-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+0x13e/0x194 lib/dump_stack.c:58
 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x139/0x17e 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 19195 Comm: syz-executor.4 Not tainted 4.14.180-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880503466c0 task.stack: ffff88821ad38000
RIP: 0010:__sanitizer_cov_trace_pc+0x23/0x50 kernel/kcov.c:68
RSP: 0018:ffff88821ad3f3c8 EFLAGS: 00000246
RAX: ffff8880503466c0 RBX: ffff8880000a0050 RCX: ffffc9000b89b000
RDX: 0000000000000001 RSI: ffffffff831ed0e3 RDI: ffff88821ad3f480
RBP: 0000000000000050 R08: 000000000000ffff R09: ffffed1043239164
R10: ffffed1043239163 R11: ffff8882191c8b1f R12: ffff8880000a004b
R13: 0000000000000000 R14: 00000000db4bbe1d R15: 000000000000004f
FS:  00007fa68d6f9700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000563fefde4908 CR3: 0000000052e76000 CR4: 00000000001406e0
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+0x285/0x310 drivers/video/fbdev/core/fbcon.c:1320
 fbcon_switch+0xcdf/0x1780 drivers/video/fbdev/core/fbcon.c:2302
 redraw_screen+0x331/0x770 drivers/tty/vt/vt.c:689
 fbcon_modechanged+0x59d/0x890 drivers/video/fbdev/core/fbcon.c:2949
 fbcon_event_notify+0x11a/0x1746 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+0xdd/0x130 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+0x42/0xb7
RIP: 0033:0x45ca29
RSP: 002b:00007fa68d6f8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004e4ac0 RCX: 000000000045ca29
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000008
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002f2 R14: 00000000004c56c8 R15: 00007fa68d6f96d4
Code: 00 00 e9 be ed ff ff 90 65 48 8b 04 25 40 ee 01 00 48 85 c0 74 1a 65 8b 15 fb a7 a7 7e 81 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 

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/05/17 21:40 linux-4.14.y ab9dfda23248 37bccd4e .config log report