INFO: task syz-executor.2:5116 blocked for more than 140 seconds. Not tainted 4.14.180-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D29904 5116 6373 0x00000004 Call Trace: schedule+0x8d/0x1b0 kernel/sched/core.c:3428 schedule_timeout+0x946/0xe40 kernel/time/timer.c:1723 do_wait_for_common kernel/sched/completion.c:91 [inline] __wait_for_common kernel/sched/completion.c:112 [inline] wait_for_common kernel/sched/completion.c:123 [inline] wait_for_completion+0x241/0x390 kernel/sched/completion.c:144 kthread_stop+0xce/0x640 kernel/kthread.c:530 ubi_detach_mtd_dev+0x1e3/0x3cc drivers/mtd/ubi/build.c:1084 ctrl_cdev_ioctl+0x14b/0x220 drivers/mtd/ubi/cdev.c:1040 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+0x42/0xb7 RIP: 0033:0x45ca29 RSP: 002b:00007f0f17a1dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004e1080 RCX: 000000000045ca29 RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003 RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000209 R14: 00000000004c44c1 R15: 00007f0f17a1e6d4 INFO: task syz-executor.1:5132 blocked for more than 140 seconds. Not tainted 4.14.180-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D29904 5132 6374 0x00000004 Call Trace: 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+0x73c/0x1470 kernel/locking/mutex.c:893 ctrl_cdev_ioctl+0x142/0x220 drivers/mtd/ubi/cdev.c:1039 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+0x42/0xb7 RIP: 0033:0x45ca29 RSP: 002b:00007f2eb926ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004e1080 RCX: 000000000045ca29 RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003 RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000209 R14: 00000000004c44c1 R15: 00007f2eb926b6d4 Showing all locks held in the system: 1 lock held by khungtaskd/1058: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548 1 lock held by in:imklog/6049: #0: (rcu_read_lock){....}, at: [] __fdget_pos+0xa6/0xc0 fs/file.c:769 2 locks held by agetty/6272: #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+0x1e4/0x16f0 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.2/5116: #0: (ubi_devices_mutex){+.+.}, at: [] ctrl_cdev_ioctl+0x142/0x220 drivers/mtd/ubi/cdev.c:1039 1 lock held by syz-executor.1/5132: #0: (ubi_devices_mutex){+.+.}, at: [] ctrl_cdev_ioctl+0x142/0x220 drivers/mtd/ubi/cdev.c:1039 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1058 Comm: khungtaskd Not tainted 4.14.180-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+0x13e/0x194 lib/dump_stack.c:58 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x139/0x17e 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: 8 Comm: rcu_preempt Not tainted 4.14.180-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8880a9854200 task.stack: ffff8880a9860000 RIP: 0010:debug_lockdep_rcu_enabled+0x26/0x90 kernel/rcu/update.c:299 RSP: 0018:ffff8880a9867a38 EFLAGS: 00000002 RAX: 0000000000000007 RBX: ffff88808db2e0a8 RCX: 1ffffffff1124598 RDX: 0000000000000000 RSI: 1ffffffff0f419ad RDI: ffffffff87a0cd68 RBP: ffffffff8a6b8760 R08: 0000000000000000 R09: 0000000000000001 R10: ffff8880a9854a88 R11: ffff8880a9854200 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f492a56a000 CR3: 000000009474d000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Call Trace: trace_lock_acquire include/trace/events/lock.h:13 [inline] lock_acquire+0x307/0x3f0 kernel/locking/lockdep.c:3997 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:160 debug_object_deactivate lib/debugobjects.c:502 [inline] debug_object_deactivate+0xe7/0x350 lib/debugobjects.c:491 debug_timer_deactivate kernel/time/timer.c:697 [inline] debug_deactivate kernel/time/timer.c:749 [inline] detach_timer kernel/time/timer.c:789 [inline] detach_if_pending+0x82/0x480 kernel/time/timer.c:808 try_to_del_timer_sync+0x9a/0xe0 kernel/time/timer.c:1180 del_timer_sync+0x17b/0x250 kernel/time/timer.c:1245 schedule_timeout+0x444/0xe40 kernel/time/timer.c:1747 rcu_gp_kthread+0xb8e/0x1ce0 kernel/rcu/tree.c:2255 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: eb ea 0f 1f 00 48 c7 c0 c4 2c 92 88 48 ba 00 00 00 00 00 fc ff df 48 89 c1 83 e0 07 48 c1 e9 03 83 c0 03 0f b6 14 11 38 d0 7c 04 <84> d2 75 46 8b 15 14 39 47 07 85 d2 74 39 48 c7 c0 e0 cf 13 88