unregister_netdevice: waiting for lo to become free. Usage count = 4 unregister_netdevice: waiting for lo to become free. Usage count = 4 unregister_netdevice: waiting for lo to become free. Usage count = 4 unregister_netdevice: waiting for lo to become free. Usage count = 4 unregister_netdevice: waiting for lo to become free. Usage count = 4 INFO: task syz-executor7:6149 blocked for more than 120 seconds. Not tainted 4.4.125-g38f41ec #63 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor7 D ffff8800b9267c38 29016 6149 1 0x00000004 ffff8800b9267c38 ffff88008cdf9800 0000000000000000 0000000000000007 ffff88008cdf9800 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8 ffff8801db31f4c0 ffff88008cdf8000 ffff88008cdf9800 0000000000000000 Call Trace: [] schedule+0x7a/0x1b0 kernel/sched/core.c:3359 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x306/0x850 kernel/locking/mutex.c:621 [] copy_net_ns+0xc7/0x190 net/core/net_namespace.c:368 [] create_new_namespaces+0x2f6/0x610 kernel/nsproxy.c:95 [] unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:190 [] SYSC_unshare kernel/fork.c:2068 [inline] [] SyS_unshare+0x3da/0x700 kernel/fork.c:2018 [] entry_SYSCALL_64_fastpath+0x22/0x9e 1 lock held by syz-executor7/6149: #0: [ 242.302932] unregister_netdevice: waiting for lo to become free. Usage count = 4 (net_mutex){+.+.+.}, at: [] copy_net_ns+0xc7/0x190 net/core/net_namespace.c:368 Sending NMI to all CPUs: NMI backtrace for cpu 0 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.125-g38f41ec #63 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffffffff84217840 task.stack: ffffffff84200000 RIP: 0010:[] [] task_on_rq_queued kernel/sched/sched.h:1124 [inline] RIP: 0010:[] [] pick_next_task_stop+0x69/0x1f0 kernel/sched/stop_task.c:33 RSP: 0018:ffffffff84207d48 EFLAGS: 00000002 RAX: 0000000000000007 RBX: ffff8801d9b16000 RCX: ffffffff84217840 RDX: 0000000000000000 RSI: ffffffff84217840 RDI: ffff8801d9b16044 RBP: ffffffff84207d68 R08: 0000000000000001 R09: ffffffff8514c100 R10: 0000000000000001 R11: 1ffffffff0840f76 R12: ffff8801db21f4c0 R13: dffffc0000000000 R14: ffffffff83853ac0 R15: ffffffff84217840 FS: 0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000c467e51000 CR3: 00000001cbff8000 CR4: 0000000000160670 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff811b9c9f ffff8801db21f4c0 ffffffff83853ac0 dffffc0000000000 ffffffff84207df0 ffffffff8376a6cb 000000381f30a27e ffffffff84207dc8 ffffffff812d5ab6 ffffffff84207d00 ffff8801db21fdb8 ffff8801db21fde0 Call Trace: [] pick_next_task kernel/sched/core.c:3195 [inline] [] __schedule+0xe3b/0x1da0 kernel/sched/core.c:3312 [] schedule+0x7a/0x1b0 kernel/sched/core.c:3359 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392 [] cpu_idle_loop kernel/sched/idle.c:279 [inline] [] cpu_startup_entry+0x2c0/0x8f0 kernel/sched/idle.c:301 [] rest_init+0x189/0x190 init/main.c:410 [] start_kernel+0x6b9/0x6ee init/main.c:682 [] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196 [] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:185 Code: 84 42 01 00 00 48 8d 7b 44 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 <84> d2 0f 85 22 01 00 00 83 7b 44 01 0f 85 0a 01 00 00 48 8d 7e NMI backtrace for cpu 1 CPU: 1 PID: 486 Comm: khungtaskd Not tainted 4.4.125-g38f41ec #63 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8800bb3c6000 task.stack: ffff8800bac08000 RIP: 0010:[] [] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline] RIP: 0010:[] [] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline] RIP: 0010:[] [] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline] RIP: 0010:[] [] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69 RSP: 0018:ffff8800bac0fcb8 EFLAGS: 00000046 RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000 RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300 RBP: ffff8800bac0fce0 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246 R13: 0000000000000003 R14: ffffffff8426f5a0 R15: 0000000000000002 FS: 0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f796397d180 CR3: 00000000b680c000 CR4: 0000000000160670 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff8426f5a0 ffffffff847f0b40 fffffbfff08fdc1c dffffc0000000000 ffff8801db31bca0 ffff8800bac0fd00 ffffffff810b9abb ffffffff839f6dc0 0000000000000003 ffff8800bac0fd60 ffffffff81d11764 ffffffff8141b993 Call Trace: [] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33 [] nmi_trigger_all_cpu_backtrace+0x4a4/0x550 lib/nmi_backtrace.c:85 [] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 [] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x6fa/0xae0 kernel/hung_task.c:238 [] kthread+0x268/0x300 kernel/kthread.c:211 [] 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