syzbot


INFO: task hung in con_flush_chars

Status: auto-closed as invalid on 2020/07/08 07:44
Reported-by: syzbot+2801c93be8a3b37973cf@syzkaller.appspotmail.com
First crash: 855d, last: 838d
similar bugs (3):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in con_flush_chars (2) 2 607d 680d 0/22 auto-closed as invalid on 2021/01/25 20:43
upstream INFO: task hung in con_flush_chars (3) 1 280d 280d 0/22 auto-closed as invalid on 2021/12/18 10:46
upstream INFO: task hung in con_flush_chars 1 803d 803d 0/22 auto-closed as invalid on 2020/07/13 22:15

Sample crash report:
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=6160 sclass=netlink_route_socket pig=15375 comm=syz-executor.3
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=6160 sclass=netlink_route_socket pig=15375 comm=syz-executor.3
Unknown ioctl 21545
base_sock_release(ffff88809282e4c0) sk=ffff88800ee17440
INFO: task getty:28974 blocked for more than 140 seconds.
      Not tainted 4.14.172-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
getty           D28304 28974      1 0x00000000
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:2864 [inline]
 con_flush_chars+0x29/0x80 drivers/tty/vt/vt.c:2856
 n_tty_write+0xbc1/0xe30 drivers/tty/n_tty.c:2350
 do_tty_write drivers/tty/tty_io.c:959 [inline]
 tty_write+0x3f0/0x700 drivers/tty/tty_io.c:1043
 __vfs_write+0xe4/0x630 fs/read_write.c:480
 vfs_write+0x192/0x4e0 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+0x42/0xb7
RIP: 0033:0x7fbb70fae370
RSP: 002b:00007ffffe42cac8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007fbb70fae370
RDX: 0000000000000009 RSI: 0000000000405be5 RDI: 0000000000000001
RBP: 00007fbb716836a8 R08: 00007ffffe42d320 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000405be5
R13: 00007ffffe42feda R14: 00007ffffe42fedd R15: 0000000000000000
INFO: task syz-executor.5:15391 blocked for more than 140 seconds.
      Not tainted 4.14.172-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D29312 15391   7523 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:891
 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:1084
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c4a9
RSP: 002b:00007f0b49137c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f0b491386d4 RCX: 000000000045c4a9
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000799 R14: 00000000004ca11a R15: 000000000076bfcc
INFO: task syz-executor.1:15389 blocked for more than 140 seconds.
      Not tainted 4.14.172-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D29504 15389   7521 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_get_cmap+0x61/0x210 drivers/tty/vt/vt.c:4021
 vt_ioctl+0xa03/0x1f00 drivers/tty/vt/vt_ioctl.c:930
 tty_ioctl+0x6c5/0x1220 drivers/tty/tty_io.c:2661
 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: 0033:0x45c4a9
RSP: 002b:00007fe066ed1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe066ed26d4 RCX: 000000000045c4a9
RDX: 0000000020000200 RSI: 0000000000004b70 RDI: 0000000000000009
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000327 R14: 00000000004c5518 R15: 000000000076bfcc
INFO: task syz-executor.1:15421 blocked for more than 140 seconds.
      Not tainted 4.14.172-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D29760 15421   7521 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_get_cmap+0x61/0x210 drivers/tty/vt/vt.c:4021
 vt_ioctl+0xa03/0x1f00 drivers/tty/vt/vt_ioctl.c:930
 tty_ioctl+0x6c5/0x1220 drivers/tty/tty_io.c:2661
 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: 0033:0x45c4a9
RSP: 002b:00007fe066e6ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe066e6f6d4 RCX: 000000000045c4a9
RDX: 0000000020000200 RSI: 0000000000004b70 RDI: 0000000000000009
RBP: 000000000076c1a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000327 R14: 00000000004c5518 R15: 000000000076c1ac

Showing all locks held in the system:
1 lock held by khungtaskd/1057:
 #0:  (tasklist_lock){.+.+}, at: [<ffffffff81465b23>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4544
1 lock held by rsyslogd/7354:
 #0:  (&f->f_pos_lock){+.+.}, at: [<ffffffff8191b3b6>] __fdget_pos+0xa6/0xc0 fs/file.c:769
2 locks held by getty/7477:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833aa792>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8339e3d4>] n_tty_read+0x1e4/0x16f0 drivers/tty/n_tty.c:2156
2 locks held by getty/7478:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833aa792>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8339e3d4>] n_tty_read+0x1e4/0x16f0 drivers/tty/n_tty.c:2156
2 locks held by getty/7479:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833aa792>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8339e3d4>] n_tty_read+0x1e4/0x16f0 drivers/tty/n_tty.c:2156
2 locks held by getty/7480:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833aa792>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8339e3d4>] n_tty_read+0x1e4/0x16f0 drivers/tty/n_tty.c:2156
2 locks held by getty/7481:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833aa792>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8339e3d4>] n_tty_read+0x1e4/0x16f0 drivers/tty/n_tty.c:2156
2 locks held by getty/7482:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833aa792>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8339e3d4>] n_tty_read+0x1e4/0x16f0 drivers/tty/n_tty.c:2156
3 locks held by getty/28974:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff833aa792>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&tty->atomic_write_lock){+.+.}, at: [<ffffffff833902fd>] tty_write_lock+0x1d/0x60 drivers/tty/tty_io.c:885
 #2:  (&tty->termios_rwsem){++++}, at: [<ffffffff8339cf17>] n_tty_write+0x187/0xe30 drivers/tty/n_tty.c:2316
1 lock held by syz-executor.5/15391:
 #0:  (&fb_info->lock){+.+.}, at: [<ffffffff8316d577>] fb_open+0xb7/0x400 drivers/video/fbdev/core/fbmem.c:1468

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

NMI backtrace for cpu 0
CPU: 0 PID: 1057 Comm: khungtaskd Not tainted 4.14.172-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: 15356 Comm: syz-executor.5 Not tainted 4.14.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888209f1e280 task.stack: ffff888205570000
RIP: 0010:writeb arch/x86/include/asm/io.h:65 [inline]
RIP: 0010:vga16fb_fillrect+0x943/0x1880 drivers/video/fbdev/vga16fb.c:923
RSP: 0018:ffff8882055773d0 EFLAGS: 00000246
RAX: 0000000000040000 RBX: ffff8880000a0050 RCX: ffffc9000822a000
RDX: 0000000000040000 RSI: ffffffff831e5da3 RDI: ffff888205577480
RBP: 0000000000000050 R08: 000000000000ffff R09: ffffed1043247c2c
R10: ffffed1043247c2b R11: ffff88821923e15f R12: ffff8880000a0007
R13: 0000000000000000 R14: 00000000d7b3c009 R15: 000000000000004f
FS:  00007f0b49159700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff195e6da20 CR3: 000000020314e000 CR4: 00000000001426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 bit_clear_margins+0x2a4/0x480 drivers/video/fbdev/core/bitblit.c:232
 fbcon_clear_margins+0x285/0x310 drivers/video/fbdev/core/fbcon.c:1317
 fbcon_switch+0xcdf/0x1780 drivers/video/fbdev/core/fbcon.c:2299
 redraw_screen+0x331/0x770 drivers/tty/vt/vt.c:688
 fbcon_modechanged+0x59d/0x890 drivers/video/fbdev/core/fbcon.c:2946
 fbcon_event_notify+0x11a/0x1746 drivers/video/fbdev/core/fbcon.c:3299
 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/0x940 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: 0033:0x45c4a9
RSP: 002b:00007f0b49158c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f0b491596d4 RCX: 000000000045c4a9
RDX: 0000000020000340 RSI: 0000000000004601 RDI: 0000000000000004
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002ef R14: 00000000004c50e2 R15: 000000000076bf2c
Code: fe 48 63 44 24 1c 44 8d 7d ff 48 89 04 24 e8 a5 e7 3b fe 45 31 ed 44 89 fa 85 ed 49 8d 5c 14 01 0f 84 b1 06 00 00 e8 8d e7 3b fe <45> 88 2c 24 49 83 c4 01 49 39 dc 75 ee e8 7b e7 3b fe 48 8b 04 

Crashes (2):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/03/10 07:43 linux-4.14.y 78d697fc93f9 35f53e45 .config log report
ci2-linux-4-14 2020/02/22 12:58 linux-4.14.y 98db2bf27b9e 2c36e7a7 .config log report