syzbot


INFO: task hung in do_con_write

Status: auto-closed as invalid on 2020/11/25 06:45
Reported-by: syzbot+bea8d157aa681e271b85@syzkaller.appspotmail.com
First crash: 1424d, last: 1367d
Similar bugs (5)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in do_con_write serial 4 1387d 1555d 0/26 auto-closed as invalid on 2020/10/06 18:58
linux-4.14 INFO: task hung in do_con_write 9 1367d 1584d 0/1 auto-closed as invalid on 2020/11/25 15:01
upstream INFO: task hung in do_con_write (2) serial 2 942d 952d 0/26 auto-closed as invalid on 2021/12/25 05:43
upstream INFO: task hung in do_con_write (4) serial 1 143d 139d 0/26 auto-obsoleted due to no activity on 2024/03/04 00:42
upstream INFO: task hung in do_con_write (3) serial 1 607d 607d 0/26 auto-obsoleted due to no activity on 2022/11/25 16:33

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 agetty:6358 blocked for more than 140 seconds.
      Not tainted 4.19.134-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
agetty          D28088  6358      1 0x00000000
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_timeout+0x92d/0xfe0 kernel/time/timer.c:1793
 __down_common kernel/locking/semaphore.c:221 [inline]
 __down+0x183/0x2a0 kernel/locking/semaphore.c:238
 down+0x57/0x80 kernel/locking/semaphore.c:62
 console_lock+0x25/0x80 kernel/printk/printk.c:2272
 do_con_write+0x11b/0x1d90 drivers/tty/vt/vt.c:2576
 con_put_char+0x96/0xe0 drivers/tty/vt/vt.c:3148
 tty_put_char+0xb7/0x150 drivers/tty/tty_io.c:2887
 __process_echoes+0x577/0x9f0 drivers/tty/n_tty.c:726
 flush_echoes drivers/tty/n_tty.c:827 [inline]
 __receive_buf drivers/tty/n_tty.c:1646 [inline]
 n_tty_receive_buf_common+0xc0c/0x2a90 drivers/tty/n_tty.c:1740
 tiocsti drivers/tty/tty_io.c:2194 [inline]
 tty_ioctl+0xff8/0x15c0 drivers/tty/tty_io.c:2580
 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: 0033:0x7f9ef1fb9017
Code: Bad RIP value.
RSP: 002b:00007fff84b88d08 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fff84b88e81 RCX: 00007f9ef1fb9017
RDX: 00007fff84b88e80 RSI: 0000000000005412 RDI: 0000000000000000
RBP: 00007fff84b88e86 R08: ffffffffffffff98 R09: 00007fff84b88d80
R10: 0000000000000000 R11: 0000000000000206 R12: 00007fff84b88d24
R13: 00007fff84b88e80 R14: 00007fff84b88d80 R15: 0000000000000000
INFO: task syz-executor.1:10933 blocked for more than 140 seconds.
      Not tainted 4.19.134-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D29520 10933   6596 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:1002 [inline]
 __mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
 fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
 chrdev_open+0x266/0x770 fs/char_dev.c:423
 do_dentry_open+0x4aa/0x1160 fs/open.c:796
 do_last fs/namei.c:3421 [inline]
 path_openat+0x793/0x2df0 fs/namei.c:3537
 do_filp_open+0x18c/0x3f0 fs/namei.c:3567
 do_sys_open+0x3b3/0x520 fs/open.c:1085
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c369
Code: 64 00 00 00 0f 11 44 24 38 48 83 c9 01 48 89 4c 24 48 e8 3a db ff ff 48 8b 44 24 50 e9 8c fe ff ff 48 8b 8c 24 a8 01 00 00 48 <8b> 94 24 b0 01 00 00 48 8b 9c 24 c8 01 00 00 e9 00 fe ff ff ba 01
RSP: 002b:00007fc76b39dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000021000 RCX: 000000000045c369
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bfe8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bfac
R13: 00007ffc58cb4d7f R14: 00007fc76b39e9c0 R15: 000000000078bfac

Showing all locks held in the system:
1 lock held by khungtaskd/1083:
 #0: 0000000010c0384a (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440
1 lock held by in:imklog/6144:
 #0: 0000000061f3b3e4 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 fs/file.c:767
3 locks held by agetty/6358:
 #0: 0000000097e38026 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #1: 000000001c2d6612 (&tty->termios_rwsem){++++}, at: n_tty_receive_buf_common+0x84/0x2a90 drivers/tty/n_tty.c:1703
 #2: 00000000380137cf (&ldata->output_lock){+.+.}, at: flush_echoes drivers/tty/n_tty.c:825 [inline]
 #2: 00000000380137cf (&ldata->output_lock){+.+.}, at: __receive_buf drivers/tty/n_tty.c:1646 [inline]
 #2: 00000000380137cf (&ldata->output_lock){+.+.}, at: n_tty_receive_buf_common+0xbce/0x2a90 drivers/tty/n_tty.c:1740
3 locks held by syz-executor.1/10907:
1 lock held by syz-executor.1/10933:
 #0: 0000000027c1293f (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457

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

NMI backtrace for cpu 1
CPU: 1 PID: 1083 Comm: khungtaskd Not tainted 4.19.134-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/0x2fe lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1a6/0x1eb 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+0x30b/0x410 kernel/kthread.c:246
 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: 10907 Comm: syz-executor.1 Not tainted 4.19.134-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0x20 kernel/kcov.c:188
Code: 66 2e 0f 1f 84 00 00 00 00 00 48 8b 0c 24 0f b7 d6 0f b7 f7 bf 03 00 00 00 e9 ec fe ff ff 66 90 66 2e 0f 1f 84 00 00 00 00 00 <48> 8b 0c 24 89 f2 89 fe bf 05 00 00 00 e9 ce fe ff ff 0f 1f 40 00
RSP: 0018:ffff88804b87f2b8 EFLAGS: 00000246
RAX: 0000000000040000 RBX: 0000000000000004 RCX: ffffc90007cd7000
RDX: 0000000000040000 RSI: 0000000000000004 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: ffff8880000a0004
R13: ffff8880000a0000 R14: 0000000000000000 R15: 000000000a3e6df5
FS:  00007fc76b3bf700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c008b1aed0 CR3: 000000008e6ed000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 vga16fb_fillrect+0x9b4/0x1940 drivers/video/fbdev/vga16fb.c:922
 bit_clear_margins+0x2d5/0x4a0 drivers/video/fbdev/core/bitblit.c:232
 fbcon_clear_margins+0x1e2/0x350 drivers/video/fbdev/core/fbcon.c:1342
 fbcon_switch+0x1038/0x1d26 drivers/video/fbdev/core/fbcon.c:2324
 redraw_screen+0x37d/0x870 drivers/tty/vt/vt.c:1015
 fbcon_modechanged+0x6e9/0x9f0 drivers/video/fbdev/core/fbcon.c:2972
 fbcon_event_notify+0x197/0x1d80 drivers/video/fbdev/core/fbcon.c:3347
 notifier_call_chain+0xc0/0x230 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+0x85/0xa0 kernel/notifier.c:325
 fb_set_var+0xc51/0xe20 drivers/video/fbdev/core/fbmem.c:1042
 do_fb_ioctl+0x3cf/0xb50 drivers/video/fbdev/core/fbmem.c:1115
 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1230
 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: 0033:0x45c369
Code: 8d 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 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fc76b3bec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000000d540 RCX: 000000000045c369
RDX: 00000000200001c0 RSI: 0000000000004601 RDI: 0000000000000005
RBP: 000000000078bf40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007ffc58cb4d7f R14: 00007fc76b3bf9c0 R15: 000000000078bf0c

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/07/28 06:45 linux-4.19.y 20b3a3dfdf6c cb93dc6a .config console log report ci2-linux-4-19
2020/06/03 15:51 linux-4.19.y 4707d8e57273 a5ce5de0 .config console log report ci2-linux-4-19
2020/06/01 07:26 linux-4.19.y 2d16cf4817bc a0331e89 .config console log report ci2-linux-4-19
* Struck through repros no longer work on HEAD.