linux-next test error: WARNING in remove_proc_entry

[syzbot <syzbot+4887e9dd9042fae2a9c2@syzkaller.appspotmail.com>]

Hello,

syzbot found the following crash on:

HEAD commit:    04c4b677 Add linux-next specific files for 20190513
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10a413c8a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b8e08a763b62ad3a
dashboard link: https://syzkaller.appspot.com/bug?extid=4887e9dd9042fae2a9c2
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4887e9dd9042fae2a9c2@syzkaller.appspotmail.com

------------[ cut here ]------------
remove_proc_entry: removing non-empty directory 'net/rpc', leaking at  
least 'use-gss-proxy'
WARNING: CPU: 0 PID: 26 at fs/proc/generic.c:681  
remove_proc_entry+0x367/0x410 fs/proc/generic.c:681
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 26 Comm: kworker/u4:2 Not tainted 5.1.0-next-20190513 #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  panic+0x2cb/0x75a kernel/panic.c:218
  __warn.cold+0x20/0x47 kernel/panic.c:575
  report_bug+0x263/0x2b0 lib/bug.c:186
  fixup_bug arch/x86/kernel/traps.c:179 [inline]
  fixup_bug arch/x86/kernel/traps.c:174 [inline]
  do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
  do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:972
RIP: 0010:remove_proc_entry+0x367/0x410 fs/proc/generic.c:681
Code: 00 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00 75 4c 49 8b 95 d0 00 00 00  
48 c7 c6 80 85 97 87 48 c7 c7 00 85 97 87 e8 c7 b1 6d ff <0f> 0b e9 4b fe  
ff ff e8 6d 54 d4 ff e9 b5 fd ff ff e8 23 55 d4 ff
RSP: 0018:ffff8880a9a8fb10 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 1ffff11015351f64 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815b20a6 RDI: ffffed1015351f54
RBP: ffff8880a9a8fbc0 R08: ffff8880a9a7c6c0 R09: ffff8880a9a7cfb0
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888099b87280
R13: ffff8880a55c77c0 R14: ffff888099b87330 R15: dffffc0000000000
  rpc_proc_exit+0x3e/0x50 net/sunrpc/stats.c:335
  sunrpc_exit_net+0x187/0x2d0 net/sunrpc/sunrpc_syms.c:73
  ops_exit_list.isra.0+0xb0/0x160 net/core/net_namespace.c:153
  cleanup_net+0x3fb/0x960 net/core/net_namespace.c:552
  process_one_work+0x98e/0x1790 kernel/workqueue.c:2268
  worker_thread+0x98/0xe40 kernel/workqueue.c:2414
  kthread+0x357/0x430 kernel/kthread.c:254
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


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