WARNING: kobject bug in netdev_queue_update_kobjects

Hello,

syzbot hit the following crash on upstream commit
661e50bc853209e41a5c14a290ca4decc43cbfd1 (Sun Mar 4 22:54:11 2018 +0000)
Linux 4.16-rc4

So far this crash happened 2 times on upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7fb6d9525a4528104e05@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for details.
If you forward the report, please keep this part and the footer.

RBP: 00007ffd67c73e10 R08: 0000000000000001 R09: 00007ffd67c70032
R10: 0000000000000000 R11: 0000000000000246 R12: 74656e2f7665642f
R13: ffffffffffffffff R14: 0000000000000008 R15: 0000000000000000
------------[ cut here ]------------
kobject_add_internal failed for tx-3 (error: -12 parent: queues)
WARNING: CPU: 1 PID: 4119 at lib/kobject.c:242 kobject_add_internal+0x3f6/0xbc0 lib/kobject.c:240
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 4119 Comm: syzkaller952529 Not tainted 4.16.0-rc4+ #341
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+0x194/0x24d lib/dump_stack.c:53
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1dc/0x200 kernel/panic.c:547
 report_bug+0x211/0x2d0 lib/bug.c:184
 fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
 fixup_bug arch/x86/kernel/traps.c:247 [inline]
 do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:986
RIP: 0010:kobject_add_internal+0x3f6/0xbc0 lib/kobject.c:240
RSP: 0018:ffff8801d2d9f488 EFLAGS: 00010286
RAX: dffffc0000000008 RBX: ffff8801d1ec0618 RCX: ffffffff815abb7e
RDX: 0000000000000000 RSI: 1ffff1003a5b3e41 RDI: 1ffff1003a5b3e16
RBP: ffff8801d2d9f580 R08: 1ffff1003a5b3dd8 R09: 0000000000000000
R10: ffff8801d2d9f248 R11: 0000000000000000 R12: 1ffff1003a5b3e97
R13: 00000000fffffff4 R14: ffff8801d0ce8d48 R15: ffffffff8684c720
 kobject_add_varg lib/kobject.c:364 [inline]
 kobject_init_and_add+0xf9/0x150 lib/kobject.c:436
 netdev_queue_add_kobject net/core/net-sysfs.c:1332 [inline]
 netdev_queue_update_kobjects+0x148/0x480 net/core/net-sysfs.c:1360
 netif_set_real_num_tx_queues+0x185/0x790 net/core/dev.c:2397
 tun_set_real_num_queues drivers/net/tun.c:638 [inline]
 tun_attach+0x7bd/0x1220 drivers/net/tun.c:863
 tun_set_queue drivers/net/tun.c:2750 [inline]
 __tun_chr_ioctl+0x8f5/0x40d0 drivers/net/tun.c:2814
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:3084
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x444229
RSP: 002b:00007ffd67c73e08 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000444229
RDX: 0000000020000200 RSI: 00000000400454d9 RDI: 0000000000000006
RBP: 00007ffd67c73e10 R08: 0000000000000001 R09: 00007ffd67c70032
R10: 0000000000000000 R11: 0000000000000246 R12: 74656e2f7665642f
R13: ffffffffffffffff R14: 0000000000000008 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug report.
Note: all commands must start from beginning of the line in the email body.