TCP: request_sock_TCPv6: Possible SYN flooding on port 20000. Sending cookies. Check SNMP counters. kworker/dying (21) used greatest stack depth: 14160 bytes left INFO: task syz-executor5:5081 blocked for more than 120 seconds. Not tainted 4.16.0-rc7+ #281 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor5 D23472 5081 4480 0x20020004 Call Trace: context_switch kernel/sched/core.c:2862 [inline] __schedule+0x8fb/0x1ec0 kernel/sched/core.c:3440 schedule+0xf5/0x430 kernel/sched/core.c:3499 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3557 __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:1461 [inline] compat_SyS_ioctl+0x151/0x2a30 fs/compat_ioctl.c:1407 do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline] do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 RIP: 0023:0xf7fc8c99 RSP: 002b:00000000f77c409c EFLAGS: 00000286 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000016 RCX: 0000000000004c00 RDX: 0000000000000017 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/868: #0: (rcu_read_lock){....}, at: [<00000000f577b76c>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000f577b76c>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<0000000024984ced>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 1 lock held by rsyslogd/4309: #0: (&f->f_pos_lock){+.+.}, at: [<00000000bd9d76a5>] __fdget_pos+0x12b/0x190 fs/file.c:765 2 locks held by getty/4399: #0: (&tty->ldisc_sem){++++}, at: [<00000000a758c874>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ec13371b>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4400: #0: (&tty->ldisc_sem){++++}, at: [<00000000a758c874>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ec13371b>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4401: #0: (&tty->ldisc_sem){++++}, at: [<00000000a758c874>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ec13371b>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4402: #0: (&tty->ldisc_sem){++++}, at: [<00000000a758c874>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ec13371b>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4403: #0: (&tty->ldisc_sem){++++}, at: [<00000000a758c874>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ec13371b>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4404: #0: (&tty->ldisc_sem){++++}, at: [<00000000a758c874>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ec13371b>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4405: #0: (&tty->ldisc_sem){++++}, at: [<00000000a758c874>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ec13371b>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 1 lock held by syz-executor5/5081: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000cdce1927>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor4/5078: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000cdce1927>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor4/5091: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000cdce1927>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 868 Comm: khungtaskd Not tainted 4.16.0-rc7+ #281 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+0x194/0x24d lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x123/0x180 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+0x3a/0x50 arch/x86/entry/entry_64.S:406 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