INFO: task syz-executor1:20263 blocked for more than 120 seconds. Not tainted 4.17.0+ #83 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor1 D23384 20263 4574 0x00000004 Call Trace: context_switch kernel/sched/core.c:2876 [inline] __schedule+0x801/0x1e30 kernel/sched/core.c:3518 schedule+0xef/0x430 kernel/sched/core.c:3562 blk_queue_enter+0x8da/0xdf0 block/blk-core.c:949 generic_make_request+0x651/0x1790 block/blk-core.c:2382 submit_bio+0xba/0x460 block/blk-core.c:2555 submit_bio_wait+0x134/0x1e0 block/bio.c:947 blkdev_issue_flush+0x204/0x300 block/blk-flush.c:548 blkdev_fsync+0x93/0xd0 fs/block_dev.c:629 vfs_fsync_range+0x140/0x220 fs/sync.c:197 vfs_fsync+0x29/0x30 fs/sync.c:211 __loop_update_dio+0x4de/0x6a0 drivers/block/loop.c:207 loop_update_dio drivers/block/loop.c:621 [inline] loop_change_fd drivers/block/loop.c:695 [inline] lo_ioctl+0xd28/0x2190 drivers/block/loop.c:1402 __blkdev_driver_ioctl block/ioctl.c:303 [inline] blkdev_ioctl+0x9b6/0x2020 block/ioctl.c:601 block_ioctl+0xee/0x130 fs/block_dev.c:1877 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701 __do_sys_ioctl fs/ioctl.c:708 [inline] __se_sys_ioctl fs/ioctl.c:706 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x455a09 RSP: 002b:00007fbe56559c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fbe5655a6d4 RCX: 0000000000455a09 RDX: 0000000000000013 RSI: 0000000000004c06 RDI: 0000000000000014 RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000002d4 R14: 00000000006f9480 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/892: #0: 00000000eddd9c47 (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: 00000000eddd9c47 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249 #1: 00000000d8f86e9f (tasklist_lock){.+.?}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470 2 locks held by rs:main Q:Reg/4403: #0: 0000000082d5b733 (&rq->lock){-.-.}, at: idle_balance kernel/sched/fair.c:9790 [inline] #0: 0000000082d5b733 (&rq->lock){-.-.}, at: pick_next_task_fair+0xffd/0x1780 kernel/sched/fair.c:6977 #1: 00000000f517229c (sb_writers#4){.+.+}, at: file_start_write include/linux/fs.h:2718 [inline] #1: 00000000f517229c (sb_writers#4){.+.+}, at: vfs_write+0x452/0x560 fs/read_write.c:548 2 locks held by getty/4495: #0: 00000000581a0a76 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000000263e4d9 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4496: #0: 00000000dbb967d3 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000cfdda9a3 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4497: #0: 00000000f7f3dc34 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000000e053e6 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4498: #0: 000000000264ded1 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000006ed8592b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4499: #0: 0000000033967e58 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000c1b25939 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4500: #0: 000000008a27efc6 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000048b1cdfa (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4501: #0: 00000000bdee12a1 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000037b90711 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 1 lock held by syz-executor1/20263: #0: 00000000956bf5a3 (&lo->lo_ctl_mutex/1){+.+.}, at: lo_ioctl+0x8d/0x2190 drivers/block/loop.c:1393 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 892 Comm: khungtaskd Not tainted 4.17.0+ #83 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+0x1b9/0x294 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0xc10/0xf60 kernel/hung_task.c:249 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54