TCP: request_sock_TCPv6: Possible SYN flooding on port 20000. Dropping request.  Check SNMP counters.
INFO: task syz-executor.2:24774 blocked for more than 140 seconds.
      Not tainted 4.9.141+ #23
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D[ 2149.662961] TCP: request_sock_TCPv6: Possible SYN flooding on port 20000. Dropping request.  Check SNMP counters.
29816 24774   2122 0x20020000
 ffff8800a277c740 ffff8801cfdf9080 ffff880090e6f900 ffff8801cedcaf80
 ffff8801db621018 ffff8800934afb50 ffffffff828075c2 0000000000000000
 ffffffff83cde790 ffff8800934afda0 0000000000005d3b ffff8801db6218f0
Call Trace:
 [<ffffffff82808aef>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff828142d5>] schedule_timeout+0x735/0xe20 kernel/time/timer.c:1771
 [<ffffffff81d4312c>] down_read_failed drivers/tty/tty_ldsem.c:241 [inline]
 [<ffffffff81d4312c>] __ldsem_down_read_nested+0x33c/0x610 drivers/tty/tty_ldsem.c:332
audit_printk_skb: 1584 callbacks suppressed
audit: type=1400 audit(1555986428.040:219823): avc:  denied  { net_admin } for  pid=2124 comm="syz-executor.3" capability=12  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.040:219824): avc:  denied  { net_admin } for  pid=2124 comm="syz-executor.3" capability=12  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.040:219825): avc:  denied  { net_admin } for  pid=2124 comm="syz-executor.3" capability=12  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.070:219826): avc:  denied  { sys_admin } for  pid=2123 comm="syz-executor.1" capability=21  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.120:219827): avc:  denied  { sys_admin } for  pid=2123 comm="syz-executor.1" capability=21  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.120:219828): avc:  denied  { sys_admin } for  pid=2123 comm="syz-executor.1" capability=21  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.150:219829): avc:  denied  { sys_admin } for  pid=2125 comm="syz-executor.4" capability=21  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.150:219830): avc:  denied  { sys_admin } for  pid=2125 comm="syz-executor.4" capability=21  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.150:219831): avc:  denied  { sys_admin } for  pid=2125 comm="syz-executor.4" capability=21  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1555986428.170:219832): avc:  denied  { sys_admin } for  pid=2123 comm="syz-executor.1" capability=21  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
 [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 [<ffffffff81d3ca85>] tty_ldisc_ref_wait+0x25/0x80 drivers/tty/tty_ldisc.c:275
 [<ffffffff81d21dfd>] tty_compat_ioctl+0x12d/0x270 drivers/tty/tty_io.c:3039
 [<ffffffff81619c8d>] C_SYSC_ioctl fs/compat_ioctl.c:1602 [inline]
 [<ffffffff81619c8d>] compat_SyS_ioctl+0x12d/0x1fd0 fs/compat_ioctl.c:1549
 [<ffffffff81006311>] do_syscall_32_irqs_on arch/x86/entry/common.c:328 [inline]
 [<ffffffff81006311>] do_fast_syscall_32+0x2f1/0xa10 arch/x86/entry/common.c:390
 [<ffffffff82818de0>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131c2c0>] rcu_read_unlock include/linux/rcupdate.h:927 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131c2c0>] rcu_lock_break kernel/hung_task.c:143 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131c2c0>] check_hung_uninterruptible_tasks kernel/hung_task.c:177 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131c2c0>] watchdog+0x310/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff813fe63f>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/2039:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor.4/6402:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor.0/14850:
 #0:  (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff81520d73>] prepare_bprm_creds+0x53/0x110 fs/exec.c:1369
2 locks held by syz-executor.2/24773:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff81d37362>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor.2/24774:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
1 lock held by syz-executor.0/28763:
 #0:  (&sb->s_type->i_mutex_key#8){+.+.+.}, at: [<ffffffff8229bd8b>] inode_lock include/linux/fs.h:766 [inline]
 #0:  (&sb->s_type->i_mutex_key#8){+.+.+.}, at: [<ffffffff8229bd8b>] __sock_release+0x8b/0x260 net/socket.c:604

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.141+ #23
 ffff8801d9907d08 ffffffff81b42e79 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810983b0 ffff8801d9907d40
 ffffffff81b4df89 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81b42e79>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b42e79>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81b4df89>] nmi_cpu_backtrace.cold.0+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81b4df1c>] nmi_trigger_cpumask_backtrace+0x12c/0x151 lib/nmi_backtrace.c:60
 [<ffffffff810984b4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8131c65d>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8131c65d>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8131c65d>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8131c65d>] watchdog+0x6ad/0xa20 kernel/hung_task.c:239
 [<ffffffff81142c3d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff82817a5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 28806 Comm: init Not tainted 4.9.141+ #23
task: ffff8800a4f7af80 task.stack: ffff8800b9a10000
RIP: 0010:[<ffffffff81207bd1>] 
c [<ffffffff81207bd1>] __lock_acquire+0x821/0x4a10 kernel/locking/lockdep.c:3342
RSP: 0018:ffff8800b9a174a0  EFLAGS: 00000082
RAX: e23209be0050c7fd RBX: ffff8800a4f7b880 RCX: 00000000e3857c20
RDX: 000000000050c7fd RSI: ffff8800a4f7b880 RDI: 0000000000000000
RBP: ffff8800b9a17648 R08: ffff8800a4f7b8a0 R09: 0000000000000001
R10: ffff8800a4f7af80 R11: 0000000000000000 R12: 00000000b4de96d5
R13: 0000000000000000 R14: 00000000424e74ef R15: 00000000be02530e
FS:  00007fb5ea9c97a0(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb5ea0dca30 CR3: 000000019fdc6000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800a4f7b81c
c 0000000000000000
c ffff8800b9a17670
c ffffffff81207a04
c
 0000000000000000
c 0000000000000000
c ffff8800b9a17548
c 0000000000000046
c
 0000000000000000
c ffffffff81ba8d8f
c ffff8800a4f7b828
c ffff8800a4f7b830
c
Call Trace:
 [<ffffffff8120c8d0>] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
 [<ffffffff8281760f>] __raw_spin_trylock include/linux/spinlock_api_smp.h:92 [inline]
 [<ffffffff8281760f>] _raw_spin_trylock+0x6f/0x90 kernel/locking/spinlock.c:135
 [<ffffffff819eaa9b>] avc_reclaim_node security/selinux/avc.c:526 [inline]
 [<ffffffff819eaa9b>] avc_alloc_node+0x12b/0x3c0 security/selinux/avc.c:559
 [<ffffffff819ebf18>] avc_insert security/selinux/avc.c:670 [inline]
 [<ffffffff819ebf18>] avc_compute_av+0x178/0x610 security/selinux/avc.c:976
 [<ffffffff819ed96d>] avc_has_perm_noaudit+0x29d/0x2f0 security/selinux/avc.c:1112
 [<ffffffff819fb3fd>] selinux_inode_permission+0x32d/0x4b0 security/selinux/hooks.c:3038
 [<ffffffff819e47e9>] security_inode_permission+0xb9/0x100 security/security.c:611
 [<ffffffff8152b9a3>] __inode_permission2+0x93/0x2d0 fs/namei.c:435
 [<ffffffff8152bc3f>] inode_permission2+0x2f/0x110 fs/namei.c:485
 [<ffffffff8153a365>] may_lookup fs/namei.c:1683 [inline]
 [<ffffffff8153a365>] link_path_walk+0x1a5/0x1230 fs/namei.c:2064
 [<ffffffff8153c1b7>] path_openat+0x1b7/0x2790 fs/namei.c:3533
 [<ffffffff81541617>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8150617d>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8150645d>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8150645d>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff810056ef>] do_syscall_64+0x19f/0x550 arch/x86/entry/common.c:285
 [<ffffffff82817893>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c