RBP: 000000000075bf20 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f004a86c6d4
R13: 00000000004c0d31 R14: 00000000004d38c8 R15: 0000000000000006
refcount_t: underflow; use-after-free.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 22175 at lib/refcount.c:187 refcount_sub_and_test lib/refcount.c:187 [inline]
WARNING: CPU: 0 PID: 22175 at lib/refcount.c:187 refcount_sub_and_test.cold+0x18/0x22 lib/refcount.c:177
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 22175 Comm: syz-executor.3 Not tainted 4.14.155-syzkaller #0
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+0x142/0x197 lib/dump_stack.c:58
 panic+0x1f9/0x42d kernel/panic.c:183
 __warn.cold+0x2f/0x2f kernel/panic.c:547
 report_bug+0x216/0x254 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:177 [inline]
 fixup_bug arch/x86/kernel/traps.c:172 [inline]
 do_error_trap+0x1bb/0x310 arch/x86/kernel/traps.c:295
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:963
RIP: 0010:refcount_sub_and_test lib/refcount.c:187 [inline]
RIP: 0010:refcount_sub_and_test.cold+0x18/0x22 lib/refcount.c:177
RSP: 0018:ffff888039f8faf8 EFLAGS: 00010286
RAX: 0000000000000026 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000040000 RSI: ffffffff814b8665 RDI: ffffed10073f1f55
RBP: ffff888039f8fb20 R08: 0000000000000026 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88807ea84ad8
R13: 0000000000000001 R14: 00000000ffffffff R15: 2000000033800100
 refcount_dec_and_test+0x1b/0x20 lib/refcount.c:212
 kref_put include/linux/kref.h:69 [inline]
 put_pid_ns+0x55/0x110 kernel/pid_namespace.c:203
 free_nsproxy+0x103/0x200 kernel/nsproxy.c:182
 switch_task_namespaces+0x98/0xb0 kernel/nsproxy.c:229
 exit_task_namespaces+0x18/0x20 kernel/nsproxy.c:234
 copy_process.part.0+0x3b59/0x6a00 kernel/fork.c:1986
 copy_process kernel/fork.c:1595 [inline]
 _do_fork+0x19e/0xce0 kernel/fork.c:2085
 SYSC_clone kernel/fork.c:2195 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2189
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45a639
RSP: 002b:00007f004a86bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f004a86bc90 RCX: 000000000045a639
RDX: 9999999999999999 RSI: 0000000000000000 RDI: 2000000033800100
RBP: 000000000075bf20 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f004a86c6d4
R13: 00000000004c0d31 R14: 00000000004d38c8 R15: 0000000000000006
Kernel Offset: disabled
Rebooting in 86400 seconds..