R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 INFO: task syz-executor6:15359 blocked for more than 120 seconds. Not tainted 4.15.0-rc6+ #159 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor6 D25048 15359 3727 0x20020004 Call Trace: context_switch kernel/sched/core.c:2799 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3375 schedule+0xf5/0x430 kernel/sched/core.c:3434 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3492 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 lo_compat_ioctl+0xab/0x140 drivers/block/loop.c:1556 compat_blkdev_ioctl+0x3ae/0x1840 block/compat_ioctl.c:406 C_SYSC_ioctl fs/compat_ioctl.c:1473 [inline] compat_SyS_ioctl+0x151/0x2a30 fs/compat_ioctl.c:1419 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline] do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129 RIP: 0023:0xf7f62c79 RSP: 002b:00000000f775e08c EFLAGS: 00000296 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000014 RCX: 0000000000004c06 RDX: 0000000000000013 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/738: #0: (rcu_read_lock){....}, at: [<00000000e986432b>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000e986432b>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000004f35b5ad>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4464 2 locks held by getty/3468: #0: (&tty->ldisc_sem){++++}, at: [<000000002f278bce>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000053008298>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3469: #0: (&tty->ldisc_sem){++++}, at: [<000000002f278bce>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000053008298>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3470: #0: (&tty->ldisc_sem){++++}, at: [<000000002f278bce>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000053008298>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3471: #0: (&tty->ldisc_sem){++++}, at: [<000000002f278bce>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000053008298>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3472: #0: (&tty->ldisc_sem){++++}, at: [<000000002f278bce>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000053008298>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3473: #0: (&tty->ldisc_sem){++++}, at: [<000000002f278bce>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000053008298>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3474: #0: (&tty->ldisc_sem){++++}, at: [<000000002f278bce>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000053008298>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by syz-executor6/15359: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000570dc794>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor5/15355: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000570dc794>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor3/15361: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000570dc794>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor3/15383: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000570dc794>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 738 Comm: khungtaskd Not tainted 4.15.0-rc6+ #159 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+0x194/0x257 lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x122/0x180 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+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc6+ #159 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:rcu_irq_enter+0xac/0x190 kernel/rcu/tree.c:1046 RSP: 0018:ffff8801db207d40 EFLAGS: 00000806 RAX: 0000000000000000 RBX: ffff8801db223760 RCX: 0000000000000000 RDX: 1ffff1003b6446ed RSI: 0000000000000001 RDI: ffff8801db223768 RBP: ffff8801db207d48 R08: 1ffff1003b645985 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff8682c340 R13: 1ffff1003b640fb1 R14: ffff8801db207e68 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000006df470 CR3: 0000000006822001 CR4: 00000000001606f0 Call Trace: irq_enter+0x13/0xd0 kernel/softirq.c:339 scheduler_ipi+0x23d/0x820 kernel/sched/core.c:1793 smp_reschedule_interrupt+0xe6/0x670 arch/x86/kernel/smp.c:277 reschedule_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:944 RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 RSP: 0018:ffffffff86807c38 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff02 RAX: dffffc0000000000 RBX: 1ffffffff0d00f8a RCX: 0000000000000000 RDX: 1ffffffff0d19078 RSI: 0000000000000001 RDI: ffffffff868c83c0 RBP: ffffffff86807c38 R08: ffffffff86662ae0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffffffff86807cf0 R14: ffffffff87030060 R15: 0000000000000000 arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline] default_idle+0xbf/0x460 arch/x86/kernel/process.c:355 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346 default_idle_call+0x36/0x90 kernel/sched/idle.c:98 cpuidle_idle_call kernel/sched/idle.c:156 [inline] do_idle+0x24a/0x3b0 kernel/sched/idle.c:246 cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:351 rest_init+0xed/0xf0 init/main.c:436 start_kernel+0x7f1/0x819 init/main.c:716 x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378 x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237 Code: c9 74 68 48 c7 c3 60 37 02 00 65 48 03 1d 75 51 a3 7e 48 8d 7b 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 04 02 <84> c0 74 08 3c 03 0f 8e 9e 00 00 00 8b 43 08 85 c0 75 2a 48 89