syzbot


INFO: task hung in do_con_write

Status: auto-closed as invalid on 2020/11/25 15:01
Reported-by: syzbot+b865d352fc4eafb7e09c@syzkaller.appspotmail.com
First crash: 925d, last: 709d
similar bugs (3):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in do_con_write 4 728d 896d 0/22 auto-closed as invalid on 2020/10/06 18:58
upstream INFO: task hung in do_con_write (2) 2 284d 294d 0/22 auto-closed as invalid on 2021/12/25 05:43
linux-4.19 INFO: task hung in do_con_write 3 709d 766d 0/1 auto-closed as invalid on 2020/11/25 06:45

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.5:8381 blocked for more than 140 seconds.
      Not tainted 4.14.189-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D29520  8381   6353 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x88b/0x1de0 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x80a/0xe90 kernel/time/timer.c:1723
 __down_common kernel/locking/semaphore.c:221 [inline]
 __down+0x16d/0x260 kernel/locking/semaphore.c:238
 down+0x57/0x80 kernel/locking/semaphore.c:62
 console_lock+0x24/0x70 kernel/printk/printk.c:2216
 do_con_write+0xd5/0x19b0 drivers/tty/vt/vt.c:2223
 con_write+0x21/0xa0 drivers/tty/vt/vt.c:2798
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x352/0xda0 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:959 [inline]
 tty_write+0x410/0x740 drivers/tty/tty_io.c:1043
 __vfs_write+0xe4/0x630 fs/read_write.c:480
 vfs_write+0x17f/0x4d0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0xf2/0x210 fs/read_write.c:582
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45c369
RSP: 002b:00007fcd66080c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000037300 RCX: 000000000045c369
RDX: 0000000000000042 RSI: 0000000020000140 RDI: 0000000000000005
RBP: 000000000078c080 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078c04c
R13: 00007ffcb4765c1f R14: 00007fcd660819c0 R15: 000000000078c04c
INFO: task syz-executor.5:8383 blocked for more than 140 seconds.
      Not tainted 4.14.189-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D29576  8383   6353 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x88b/0x1de0 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+0x669/0x1310 kernel/locking/mutex.c:893
 fb_open+0xfb/0x4a0 drivers/video/fbdev/core/fbmem.c:1468
 chrdev_open+0x23c/0x6d0 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+0x628/0x2970 fs/namei.c:3569
 do_filp_open+0x179/0x3c0 fs/namei.c:3603
 do_sys_open+0x296/0x410 fs/open.c:1081
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45c369
RSP: 002b:00007fcd6603ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000021000 RCX: 000000000045c369
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078c1c8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078c18c
R13: 00007ffcb4765c1f R14: 00007fcd6603f9c0 R15: 000000000078c18c

Showing all locks held in the system:
1 lock held by khungtaskd/1061:
 #0:  (tasklist_lock){.+.+}, at: [<ffffffff81477894>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
1 lock held by in:imklog/6026:
 #0:  (&f->f_pos_lock){+.+.}, at: [<ffffffff8193b13b>] __fdget_pos+0x1fb/0x2b0 fs/file.c:769
4 locks held by syz-executor.5/8381:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff8343c652>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&tty->atomic_write_lock){+.+.}, at: [<ffffffff83424bad>] tty_write_lock drivers/tty/tty_io.c:885 [inline]
 #1:  (&tty->atomic_write_lock){+.+.}, at: [<ffffffff83424bad>] do_tty_write drivers/tty/tty_io.c:908 [inline]
 #1:  (&tty->atomic_write_lock){+.+.}, at: [<ffffffff83424bad>] tty_write+0x22d/0x740 drivers/tty/tty_io.c:1043
 #2:  (&tty->termios_rwsem){++++}, at: [<ffffffff834304da>] n_tty_write+0x18a/0xda0 drivers/tty/n_tty.c:2316
 #3:  (&ldata->output_lock){+.+.}, at: [<ffffffff8343078f>] process_output_block drivers/tty/n_tty.c:550 [inline]
 #3:  (&ldata->output_lock){+.+.}, at: [<ffffffff8343078f>] n_tty_write+0x43f/0xda0 drivers/tty/n_tty.c:2333
1 lock held by syz-executor.5/8383:
 #0:  (&fb_info->lock){+.+.}, at: [<ffffffff831f8b6b>] fb_open+0xfb/0x4a0 drivers/video/fbdev/core/fbmem.c:1468

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

NMI backtrace for cpu 0
CPU: 0 PID: 1061 Comm: khungtaskd Not tainted 4.14.189-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+0x5b9/0xb40 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: 8357 Comm: syz-executor.5 Not tainted 4.14.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880519a8540 task.stack: ffff888051540000
RIP: 0010:__sanitizer_cov_trace_pc+0x23/0x50 kernel/kcov.c:68
RSP: 0018:ffff888051547328 EFLAGS: 00000246
RAX: ffff8880519a8540 RBX: ffff8880000a0140 RCX: ffffc90009aca000
RDX: 0000000000000001 RSI: ffffffff832385f4 RDI: 0000000000000a00
RBP: 0000000000000000 R08: 0000000000000a00 R09: 0000000000000040
R10: ffff88821926305f R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fcd660c3700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3f3d0a1000 CR3: 000000009fb1b000 CR4: 00000000001426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 bitfill_aligned drivers/video/fbdev/core/cfbfillrect.c:74 [inline]
 bitfill_aligned+0x10a/0x190 drivers/video/fbdev/core/cfbfillrect.c:35
 cfb_fillrect+0x3c7/0x710 drivers/video/fbdev/core/cfbfillrect.c:327
 vga16fb_fillrect+0x5fa/0x1820 drivers/video/fbdev/vga16fb.c:951
 bit_clear_margins+0x2a4/0x480 drivers/video/fbdev/core/bitblit.c:232
 fbcon_clear_margins+0x1bb/0x300 drivers/video/fbdev/core/fbcon.c:1320
 fbcon_switch+0xdb4/0x1b1f drivers/video/fbdev/core/fbcon.c:2302
 redraw_screen+0x32c/0x790 drivers/tty/vt/vt.c:689
 fbcon_modechanged+0x68a/0x980 drivers/video/fbdev/core/fbcon.c:2949
 fbcon_event_notify+0x107/0x1760 drivers/video/fbdev/core/fbcon.c:3302
 notifier_call_chain+0x108/0x1a0 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+0xac5/0xc90 drivers/video/fbdev/core/fbmem.c:1054
 do_fb_ioctl+0x36d/0xa70 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/0xff0 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: 0033:0x45c369
RSP: 002b:00007fcd660c2c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000000d540 RCX: 000000000045c369
RDX: 00000000200001c0 RSI: 0000000000004601 RDI: 000000000000000b
RBP: 000000000078bf40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007ffcb4765c1f R14: 00007fcd660c39c0 R15: 000000000078bf0c
Code: 00 00 e9 c6 ed ff ff 90 65 48 8b 04 25 40 ee 01 00 48 85 c0 74 1a 65 8b 15 4b 57 a6 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 (9):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/07/28 15:00 linux-4.14.y 69b94dd6dcd1 cb93dc6a .config log report
ci2-linux-4-14 2020/06/28 19:17 linux-4.14.y b850307b279c a2cdad9d .config log report
ci2-linux-4-14 2020/06/15 07:27 linux-4.14.y b850307b279c 2a22c77a .config log report
ci2-linux-4-14 2020/05/29 06:02 linux-4.14.y 4f68020fef1c d19ed305 .config log report
ci2-linux-4-14 2020/05/17 13:29 linux-4.14.y ab9dfda23248 37bccd4e .config log report
ci2-linux-4-14 2020/04/12 13:52 linux-4.14.y 4520f06b03ae 36b0b050 .config log report
ci2-linux-4-14 2020/03/17 02:39 linux-4.14.y 12cd844a39ed 749688d2 .config log report
ci2-linux-4-14 2020/03/15 21:11 linux-4.14.y 12cd844a39ed 749688d2 .config log report
ci2-linux-4-14 2019/12/25 03:16 linux-4.14.y e1f7d50ae3a3 be5c2c81 .config log report