INFO: task syz-executor.4:9938 blocked for more than 143 seconds. Not tainted 5.6.0-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D27296 9938 7609 0x00000004 Call Trace: schedule+0xd0/0x2a0 kernel/sched/core.c:4168 schedule_timeout+0x55b/0x850 kernel/time/timer.c:1874 __down_common kernel/locking/semaphore.c:220 [inline] __down+0x176/0x2c0 kernel/locking/semaphore.c:237 down+0x57/0x80 kernel/locking/semaphore.c:61 console_lock+0x25/0x80 kernel/printk/printk.c:2286 do_con_write.part.0+0x95/0x1dc0 drivers/tty/vt/vt.c:2590 do_con_write drivers/tty/vt/vt.c:2587 [inline] con_write+0x41/0xe0 drivers/tty/vt/vt.c:3153 process_output_block drivers/tty/n_tty.c:595 [inline] n_tty_write+0x3f0/0xf90 drivers/tty/n_tty.c:2333 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x495/0x800 drivers/tty/tty_io.c:1046 __vfs_write+0x76/0x100 fs/read_write.c:494 vfs_write+0x268/0x5d0 fs/read_write.c:558 ksys_write+0x12d/0x250 fs/read_write.c:611 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x45c889 Code: 60 48 85 c9 74 1a 8b 54 24 24 85 d2 74 12 8b 5c 24 68 0f b7 0c 59 81 e1 ff 7f 00 00 39 d1 75 30 48 8b 4c 24 28 48 8b 54 24 40 <48> 8b 4c ca 08 48 03 48 10 48 8b 84 24 88 00 00 00 48 89 08 c6 84 RSP: 002b:00007fbf46600c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fbf466016d4 RCX: 000000000045c889 RDX: 00000000000007c3 RSI: 0000000020001340 RDI: 000000000000000b RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000cdc R14: 00000000004cf042 R15: 000000000076bf0c Showing all locks held in the system: 1 lock held by khungtaskd/1135: #0: ffffffff899bbbc0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5743 1 lock held by in:imklog/6805: #0: ffff888093fecdb0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:826 4 locks held by syz-executor.4/9938: #0: ffff88809fc77098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 #1: ffff88809fc77130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock+0x1e/0x80 drivers/tty/tty_io.c:888 #2: ffff88809fc772e8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_write+0x1b2/0xf90 drivers/tty/n_tty.c:2316 #3: ffffc90000f10378 (&ldata->output_lock){+.+.}-{3:3}, at: process_output_block drivers/tty/n_tty.c:550 [inline] #3: ffffc90000f10378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0x50c/0xf90 drivers/tty/n_tty.c:2333 2 locks held by syz-executor.3/9942: ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1135 Comm: khungtaskd Not tainted 5.6.0-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+0x188/0x20d lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x231/0x27e lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline] watchdog+0xa8c/0x1010 kernel/hung_task.c:289 kthread+0x388/0x470 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 9942 Comm: syz-executor.3 Not tainted 5.6.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:write_comp_data+0x1e/0x70 kernel/kcov.c:208 Code: 48 89 11 c3 0f 1f 84 00 00 00 00 00 65 4c 8b 04 25 00 1f 02 00 65 8b 05 f8 ec 8e 7e a9 00 01 1f 00 75 51 41 8b 80 d8 13 00 00 <83> f8 03 75 45 49 8b 80 e0 13 00 00 45 8b 80 dc 13 00 00 4c 8b 08 RSP: 0018:ffffc90002257590 EFLAGS: 00000246 RAX: 0000000000000002 RBX: 0000000000000050 RCX: ffffffff83bd61fa RDX: 0000000000000006 RSI: 0000000000000050 RDI: 0000000000000004 RBP: 0000000000000006 R08: ffff8880a3554100 R09: ffffed1014778f4c R10: ffff8880a3bc7a5f R11: ffffed1014778f4b R12: ffff8880000a0006 R13: ffff8880000a0000 R14: 0000000000000000 R15: 00000000f1529e02 FS: 00007f59595b8700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb4914a3000 CR3: 00000000a1b04000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: vga16fb_fillrect+0x9da/0x1960 drivers/video/fbdev/vga16fb.c:922 bit_clear_margins+0x2d5/0x4a0 drivers/video/fbdev/core/bitblit.c:232 fbcon_clear_margins+0x1de/0x240 drivers/video/fbdev/core/fbcon.c:1378 fbcon_switch+0xd21/0x1740 drivers/video/fbdev/core/fbcon.c:2360 redraw_screen+0x2ae/0x770 drivers/tty/vt/vt.c:1009 fbcon_modechanged+0x5c3/0x790 drivers/video/fbdev/core/fbcon.c:2997 fbcon_update_vcs+0x3a/0x50 drivers/video/fbdev/core/fbcon.c:3044 fb_set_var+0xad0/0xd40 drivers/video/fbdev/core/fbmem.c:1056 do_fb_ioctl+0x390/0x6e0 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1185 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x11a/0x180 fs/ioctl.c:763 __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl fs/ioctl.c:770 [inline] __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x45c889 Code: ad 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f59595b7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f59595b86d4 RCX: 000000000045c889 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000002ee R14: 00000000004c54bc R15: 000000000076bf0c