syzbot


INFO: task hung in vcs_open

Status: auto-closed as invalid on 2020/09/30 10:12
Reported-by: syzbot+7fddf746887eadd5f171@syzkaller.appspotmail.com
First crash: 840d, last: 757d
similar bugs (4):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in vcs_open (3) 1 492d 492d 0/22 auto-closed as invalid on 2021/05/22 19:06
upstream INFO: task hung in vcs_open 32 663d 796d 0/22 closed as dup on 2020/08/05 10:53
upstream INFO: task hung in vcs_open (2) 1 643d 643d 0/22 auto-closed as invalid on 2020/12/23 12:34
linux-4.19 INFO: task hung in vcs_open 11 599d 912d 0/1 auto-closed as invalid on 2021/03/07 01:31

Sample crash report:
RDX: 0492492492492805 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 00000000000008de R14: 00000000004cba68 R15: 00007fefc12786d4
NOHZ: local_softirq_pending 08
INFO: task syz-executor.1:19082 blocked for more than 140 seconds.
      Not tainted 4.14.182-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D29584 19082   6343 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x8a6/0x1d70 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x86c/0xe50 kernel/time/timer.c:1723
 __down_common kernel/locking/semaphore.c:221 [inline]
 __down+0x17f/0x280 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+0x44b/0xec0 fs/open.c:777
 vfs_open+0x105/0x220 fs/open.c:888
 do_last fs/namei.c:3428 [inline]
 path_openat+0xb68/0x2aa0 fs/namei.c:3569
 do_filp_open+0x18e/0x250 fs/namei.c:3603
 do_sys_open+0x292/0x3e0 fs/open.c:1081
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x416861
RSP: 002b:00007f8c4e0657a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 6666666666666667 RCX: 0000000000416861
RDX: 0000000000000000 RSI: 0000000000060001 RDI: 00007f8c4e065850
RBP: 000000000078bf00 R08: 000000000000000f R09: 0000000000000000
R10: 00007f8c4e0669d0 R11: 0000000000000293 R12: 00000000ffffffff
R13: 0000000000000c20 R14: 00000000004ce71f R15: 00007f8c4e0666d4

Showing all locks held in the system:
1 lock held by khungtaskd/1057:
 #0:  (tasklist_lock){.+.+}, at: [<ffffffff8146c8d0>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
1 lock held by in:imklog/6015:
 #0:  (&f->f_pos_lock){+.+.}, at: [<ffffffff8191f176>] __fdget_pos+0xa6/0xc0 fs/file.c:769
2 locks held by agetty/6011:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833be8c2>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff833b9ea4>] n_tty_read+0x1e4/0x16e0 drivers/tty/n_tty.c:2156
2 locks held by agetty/6055:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833be8c2>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff833b9ea4>] n_tty_read+0x1e4/0x16e0 drivers/tty/n_tty.c:2156

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

NMI backtrace for cpu 0
CPU: 0 PID: 1057 Comm: khungtaskd Not tainted 4.14.182-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+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: 19079 Comm: syz-executor.5 Not tainted 4.14.182-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880499ae400 task.stack: ffff8882132f0000
RIP: 0010:vga16fb_fillrect+0x961/0x1880 drivers/video/fbdev/vga16fb.c:926
RSP: 0018:ffff8882132f73e0 EFLAGS: 00000293
RAX: ffffffffffffffd8 RBX: ffff8880000a0028 RCX: ffffc90008d5b000
RDX: 0000000000040000 RSI: ffffffff831faea5 RDI: ffff8882132f7490
RBP: 0000000000000028 R08: 000000000000ffff R09: ffffed1043244acc
R10: ffffed1043244acb R11: ffff88821922565f R12: ffff8880000a0028
R13: 0000000000000000 R14: 00000000b3f1f31e R15: 0000000000000027
FS:  00007f1f4f581700(0000) GS:ffff8880aed00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c0106c8860 CR3: 0000000093df6000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 bit_clear_margins+0x2a4/0x480 drivers/video/fbdev/core/bitblit.c:232
 fbcon_clear_margins+0x274/0x300 drivers/video/fbdev/core/fbcon.c:1320
 fbcon_switch+0xc4e/0x1700 drivers/video/fbdev/core/fbcon.c:2302
 redraw_screen+0x332/0x760 drivers/tty/vt/vt.c:689
 fbcon_modechanged+0x552/0x800 drivers/video/fbdev/core/fbcon.c:2949
 fbcon_event_notify+0x11a/0x1750 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+0xda/0x120 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+0x46/0xbb
RIP: 0033:0x45ca69
RSP: 002b:00007f1f4f580c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004e4b00 RCX: 000000000045ca69
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002f2 R14: 00000000004c5708 R15: 00007f1f4f5816d4
Code: 14 01 0f 84 b1 06 00 00 e8 dd f6 3a fe 45 88 2c 24 49 83 c4 01 49 39 dc 75 ee e8 cb f6 3a fe 48 8b 04 24 41 83 ee 01 41 83 fe ff <4c> 8d 24 03 75 bf e9 8f fc ff ff e8 cf 39 64 fe e9 d1 f6 ff ff 

Crashes (3):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/06/02 10:11 linux-4.14.y 4f68020fef1c a0331e89 .config log report
ci2-linux-4-14 2020/04/12 08:11 linux-4.14.y 4520f06b03ae a8c6a3f8 .config log report
ci2-linux-4-14 2020/03/10 21:45 linux-4.14.y 78d697fc93f9 35f53e45 .config log report