INFO: task syz-executor.4:15896 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.4 D28184 15896 6907 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:00007fa9508d5c78 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: 00007ffdfb5b6daf R14: 00007fa9508d69c0 R15: 000000000078bfac INFO: task syz-executor.2:15901 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.2 D29520 15901 6662 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:00007f338e951c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000000000021000 RCX: 000000000045c369 RDX: 0000000000080000 RSI: 0000000020000180 RDI: ffffffffffffff9c RBP: 000000000078bf48 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c R13: 00007ffcb5c418ff R14: 00007f338e9529c0 R15: 000000000078bf0c Showing all locks held in the system: 1 lock held by khungtaskd/1084: #0: 00000000b8ba5857 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440 1 lock held by in:imklog/6152: #0: 000000001a4f1274 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 fs/file.c:767 3 locks held by syz-executor.4/15890: 1 lock held by syz-executor.4/15896: #0: 000000008ef15d4e (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457 1 lock held by syz-executor.2/15901: #0: 000000008ef15d4e (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1084 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: 15890 Comm: syz-executor.4 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_cmp4+0x4/0x20 kernel/kcov.c:162 Code: b6 f7 31 ff eb 80 48 8b 0c 24 0f b7 d6 0f b7 f7 bf 02 00 00 00 e9 6c ff ff ff 66 90 66 2e 0f 1f 84 00 00 00 00 00 48 8b 0c 24 <89> f2 89 fe bf 04 00 00 00 e9 4e ff ff ff 0f 1f 40 00 66 2e 0f 1f RSP: 0018:ffff8881eac572b8 EFLAGS: 00000286 RAX: 0000000000040000 RBX: 0000000000000032 RCX: ffffffff8385e384 RDX: 0000000000040000 RSI: 0000000000000012 RDI: 0000000000000032 RBP: 0000000000000012 R08: 0000000000000001 R09: 0000000000000032 R10: 0000000000000004 R11: 0000000000000000 R12: ffff8880000a0012 R13: ffff8880000a0000 R14: 0000000000000000 R15: 00000000e3aea752 FS: 00007fa9508f7700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000056314ed73f3f CR3: 0000000204515000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: vga16fb_fillrect+0x9d4/0x1940 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:00007fa9508f6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000000d540 RCX: 000000000045c369 RDX: 00000000200001c0 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 000000000078bf40 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c R13: 00007ffdfb5b6daf R14: 00007fa9508f79c0 R15: 000000000078bf0c