unregister_netdevice: waiting for lo to become free. Usage count = 28
unregister_netdevice: waiting for lo to become free. Usage count = 28
unregister_netdevice: waiting for lo to become free. Usage count = 28
unregister_netdevice: waiting for lo to become free. Usage count = 28
unregister_netdevice: waiting for lo to become free. Usage count = 28
INFO: task syz-executor0:5280 blocked for more than 120 seconds.
      Not tainted 4.4.125-g38f41ec #21
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D ffff8801b6dafbc8 28888  5280      1 0x20020004
 ffff8801b6dafbc8 ffff8801cefe3000 0000000000000000 0000000000000007
 ffff8801cefe3000 ffff8801db21fdb8 ffff8801db21fde0 ffff8801db21f4d8
 ffff8801db21f4c0 ffff8801b7e1c800 ffff8801cefe3000 0000000000000000
Call Trace:
 [<ffffffff8376b82a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff8376c023>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392
 [<ffffffff837705e6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff837705e6>] mutex_lock_nested+0x306/0x850 kernel/locking/mutex.c:621
 [<ffffffff82e33be7>] copy_net_ns+0xc7/0x190 net/core/net_namespace.c:368
 [<ffffffff81193166>] create_new_namespaces+0x2f6/0x610 kernel/nsproxy.c:95
 [<ffffffff81193a1e>] unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:190
 [<ffffffff8112cc8a>] SYSC_unshare kernel/fork.c:2068 [inline]
 [<ffffffff8112cc8a>] SyS_unshare+0x3da/0x700 kernel/fork.c:2018
 [<ffffffff81006d91>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d91>] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459
 [<ffffffff8377b2aa>] sysenter_flags_fixed+0xd/0x17
1 lock held by syz-executor0/5280:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82e33be7>] copy_net_ns+0xc7/0x190 net/core/net_namespace.c:368
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 487 Comm: khungtaskd Not tainted 4.4.125-g38f41ec #21
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb056000 task.stack: ffff8801d9388000
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8801d938fcb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8801d938fce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426f5a0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe90fcb2000 CR3: 00000001d38d0000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426f5a0 ffffffff847f0b40 fffffbfff08fdc1c dffffc0000000000
 ffff8801db31bca0 ffff8801d938fd00 ffffffff810b9abb ffffffff839f6dc0
 0000000000000003 ffff8801d938fd60 ffffffff81d11764 ffffffff8141b993
Call Trace:
 [<ffffffff810b9abb>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d11764>] nmi_trigger_all_cpu_backtrace+0x4a4/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b9b54>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813695ca>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813695ca>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813695ca>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813695ca>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff81190b48>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff83779d95>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 2b 33 17 00 4c 89 e7 57 9d 0f 1f 
NMI backtrace for cpu 1
CPU: 1 PID: 3644 Comm: rsyslogd Not tainted 4.4.125-g38f41ec #21
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800ae5c6000 task.stack: ffff8801d4400000
RIP: 0010:[<ffffffff811a45fc>]  [<ffffffff811a45fc>] finish_task_switch+0x1ec/0x660 kernel/sched/core.c:2686
RSP: 0018:ffff8801d4407a80  EFLAGS: 00000286
RAX: 0000000080000001 RBX: ffff8801db31f4c0 RCX: 0000000000000000
RDX: 0000000000000002 RSI: ffff8800ae5c68e0 RDI: ffffffff85702600
RBP: ffff8801d4407ac8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d9b49800
R13: ffff8800af5ea300 R14: 0000000000000000 R15: ffff8800ae5c6000
FS:  00007f89e3f4c700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000794b10 CR3: 00000001d38d0000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff811a45cb ffffffff8376a4a0 06ce498bddcf6407 ffff8801db31f4d8
 ffff8801db31f4d8 ffff8800af5ea300 ffff8800af5ea300 ffff8801d9b49ca0
 ffffffff847ecfb8 ffff8801d4407b50 ffffffff8376a542 0000000000000246
Call Trace:
 [<ffffffff8376a542>] context_switch kernel/sched/core.c:2811 [inline]
 [<ffffffff8376a542>] __schedule+0xcb2/0x1da0 kernel/sched/core.c:3330
 [<ffffffff8376b82a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff812692d2>] do_syslog+0x592/0xae0 kernel/printk/printk.c:1327
 [<ffffffff816913f4>] kmsg_read+0x74/0xa0 fs/proc/kmsg.c:39
 [<ffffffff8166674f>] proc_reg_read+0xef/0x170 fs/proc/inode.c:202
 [<ffffffff8151d873>] __vfs_read+0x103/0x440 fs/read_write.c:432
 [<ffffffff8151f713>] vfs_read+0x123/0x3a0 fs/read_write.c:454
 [<ffffffff81522059>] SYSC_read fs/read_write.c:569 [inline]
 [<ffffffff81522059>] SyS_read+0xd9/0x1b0 fs/read_write.c:562
 [<ffffffff83779965>] entry_SYSCALL_64_fastpath+0x22/0x9e
Code: d2 4c 89 7b 10 31 f6 41 b8 01 00 00 00 48 c7 04 24 cb 45 1a 81 48 8d 7b 18 e8 61 95 09 00 48 89 df e8 99 48 5d 02 4d 85 ed 74 07 <f0> 41 ff 4d 4c 74 18 49 83 fe 40 74 20 48 83 c4 20 48 89 d8 5b