INFO: task syz-executor.0:30315 blocked for more than 140 seconds. Not tainted 4.14.184-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28928 30315 6375 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_preempt_disabled+0xf/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x5f0/0x1430 kernel/locking/mutex.c:893 fb_release+0x4e/0x140 drivers/video/fbdev/core/fbmem.c:1497 __fput+0x25f/0x7a0 fs/file_table.c:210 task_work_run+0x113/0x190 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x416721 RSP: 002b:00007fff2316fca0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000416721 RDX: 0000001b31b20000 RSI: ffffffff8640008a RDI: 0000000000000003 RBP: 0000000000000001 R08: ffffffff810071c6 R09: 0000000080682160 R10: 00007fff2316fd90 R11: 0000000000000293 R12: 000000000078c900 R13: 000000000078c900 R14: ffffffffffffffff R15: 000000000078bfac Showing all locks held in the system: 1 lock held by khungtaskd/1057: #0: (tasklist_lock){.+.?}, at: [] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548 1 lock held by in:imklog/5986: #0: (&f->f_pos_lock){+.+.}, at: [] __fdget_pos+0xa6/0xc0 fs/file.c:769 1 lock held by syz-executor.0/30315: #0: (&fb_info->lock){+.+.}, at: [] fb_release+0x4e/0x140 drivers/video/fbdev/core/fbmem.c:1497 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1057 Comm: khungtaskd Not tainted 4.14.184-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: 30323 Comm: syz-executor.2 Not tainted 4.14.184-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8880a87924c0 task.stack: ffff8880a9858000 RIP: 0010:__sanitizer_cov_trace_pc+0x29/0x50 kernel/kcov.c:71 RSP: 0018:ffff8880a985f3d8 EFLAGS: 00000246 RAX: ffff8880a87924c0 RBX: ffff8880000a0050 RCX: ffffc9000af24000 RDX: 0000000000000001 RSI: ffffffff831f9ef3 RDI: ffff8880a985f490 RBP: 0000000000000050 R08: 000000000000ffff R09: ffffed1014bdaf74 R10: ffffed1014bdaf73 R11: ffff8880a5ed7b9f R12: ffff8880000a0032 R13: 0000000000000000 R14: 00000000d37278b1 R15: 000000000000004f FS: 00007fcf6cad7700(0000) GS:ffff8880aed00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055aec0d999f8 CR3: 000000008454b000 CR4: 00000000001426e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Call Trace: writeb arch/x86/include/asm/io.h:65 [inline] vga16fb_fillrect+0x943/0x1880 drivers/video/fbdev/vga16fb.c:923 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: 0033:0x45cba9 RSP: 002b:00007fcf6cad6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004e5c80 RCX: 000000000045cba9 RDX: 0000000020000080 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000002fe R14: 00000000004c5931 R15: 00007fcf6cad76d4 Code: ff 90 65 48 8b 04 25 40 ee 01 00 48 85 c0 74 1a 65 8b 15 db 47 a7 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 00 00 48 8b 11 48