INFO: task syz-executor046:8416 blocked for more than 140 seconds. Not tainted 4.14.209-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor046 D28912 8416 7986 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:1724 __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:2219 do_fb_ioctl+0x2e7/0xa70 drivers/video/fbdev/core/fbmem.c:1121 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: 0033:0x445189 RSP: 002b:00007ffcec01b8b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000020000080 RCX: 0000000000445189 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000000bed59 R08: 00000000004002e0 R09: 00000000004002e0 R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000402350 R13: 00000000004023e0 R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 1 lock held by khungtaskd/1532: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548 1 lock held by in:imklog/7651: #0: (&f->f_pos_lock){+.+.}, at: [] __fdget_pos+0x1fb/0x2b0 fs/file.c:769 2 locks held by agetty/7701: #0: (&tty->ldisc_sem){++++}, at: [] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e3/0x1680 drivers/tty/n_tty.c:2156 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1532 Comm: khungtaskd Not tainted 4.14.209-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 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 22 Comm: kworker/u4:1 Not tainted 4.14.209-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_unbound flush_to_ldisc task: ffff8880b55f85c0 task.stack: ffff8880b5600000 RIP: 0010:__sanitizer_cov_trace_pc+0x23/0x50 kernel/kcov.c:68 RSP: 0018:ffff8880b56075f8 EFLAGS: 00000246 RAX: ffff8880b55f85c0 RBX: ffff8880000a0035 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff8880b5607690 RDI: ffff8880b56076a0 RBP: 0000000000000050 R08: 0000000000000010 R09: 0000000000000280 R10: ffffffff8c8ad014 R11: 0000000000000000 R12: 00000000aa32f28e R13: ffffffffffffffb0 R14: ffff8880000a0050 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000006cf090 CR3: 00000000b3a82000 CR4: 00000000001406f0 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+0x910/0x1820 drivers/video/fbdev/vga16fb.c:923 bit_clear+0x32a/0x450 drivers/video/fbdev/core/bitblit.c:74 fbcon_clear+0x558/0x650 drivers/video/fbdev/core/fbcon.c:1236 fbcon_scroll+0x3c1/0x31e0 drivers/video/fbdev/core/fbcon.c:1734 con_scroll+0x2c5/0x360 drivers/tty/vt/vt.c:327 lf+0x226/0x270 drivers/tty/vt/vt.c:1141 do_con_write+0xf9b/0x19b0 drivers/tty/vt/vt.c:2414 con_put_char+0x78/0xa0 drivers/tty/vt/vt.c:2815 tty_put_char+0xa3/0x120 drivers/tty/tty_io.c:2879 do_output_char+0x126/0x750 drivers/tty/n_tty.c:488 __process_echoes+0x313/0x8c0 drivers/tty/n_tty.c:739 flush_echoes drivers/tty/n_tty.c:829 [inline] __receive_buf drivers/tty/n_tty.c:1648 [inline] n_tty_receive_buf_common+0x9a3/0x25a0 drivers/tty/n_tty.c:1742 tty_ldisc_receive_buf+0x9e/0x170 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x6e/0xa0 drivers/tty/tty_port.c:37 receive_buf drivers/tty/tty_buffer.c:475 [inline] flush_to_ldisc+0x1dd/0x3f0 drivers/tty/tty_buffer.c:527 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: 00 00 e9 c6 ed ff ff 90 65 48 8b 04 25 80 df 01 00 48 85 c0 74 1a 65 8b 15 bb 9f aa 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