WARNING in kernfs_get

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    9a5682765a2e Merge branch 'x86-urgent-for-linus' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1624858e400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
dashboard link: https://syzkaller.appspot.com/bug?extid=3dcb532381f98c86aeb1
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12657f0a400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=117728ae400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3dcb532381f98c86aeb1@xxxxxxxxxxxxxxxxxxxxxxxxx

WARNING: CPU: 0 PID: 5659 at fs/kernfs/dir.c:494  
kernfs_get.part.8+0x131/0x160 fs/kernfs/dir.c:494
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 5659 Comm: syz-executor154 Not tainted 4.19.0-rc2+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
 panic+0x238/0x4e7 kernel/panic.c:184
 __warn.cold.8+0x163/0x1ba kernel/panic.c:536
 report_bug+0x254/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:993
RIP: 0010:kernfs_get.part.8+0x131/0x160 fs/kernfs/dir.c:494
Code: 44 05 00 00 00 00 00 48 8b 45 d0 65 48 33 04 25 28 00 00 00 75 2f 48  
83 c4 60 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 df 1c 87 ff <0f> 0b eb b1 4c  
89 e7 e8 d3 83 ca ff eb 81 48 89 df e8 29 83 ca ff
RSP: 0018:ffff8801d892f500 EFLAGS: 00010293
RAX: ffff8801c5f56640 RBX: ffff8801c541b8c0 RCX: ffffffff81f7b391
kobject: 'bluetooth' (00000000076788a3): kobject_add_internal:  
parent: 'virtual', set: '(null)'
RDX: 0000000000000000 RSI: ffffffff81f7b3e1 RDI: 0000000000000005
RBP: ffff8801d892f588 R08: ffff8801c5f56640 R09: ffffed0038a83718
R10: ffffed0038a83718 R11: ffff8801c541b8c3 R12: 1ffff1003b125ea4
R13: 1ffff1003b125ea0 R14: 0000000000000000 R15: ffff8801d892f560
 kernfs_get fs/kernfs/dir.c:493 [inline]
 kernfs_new_node+0xb4/0x120 fs/kernfs/dir.c:698
 kernfs_create_dir_ns+0x4d/0x160 fs/kernfs/dir.c:1021
 sysfs_create_dir_ns+0x19b/0x340 fs/sysfs/dir.c:58
kobject: 'hci1' (000000003c3c3740): kobject_add_internal:  
parent: 'bluetooth', set: 'devices'
 create_dir lib/kobject.c:88 [inline]
 kobject_add_internal+0x440/0xb60 lib/kobject.c:247
kobject: 'hci3' (00000000e8906dbf): kobject_add_internal:  
parent: 'bluetooth', set: 'devices'
kobject: 'hci3' (00000000e8906dbf): kobject_uevent_env
 kobject_add_varg lib/kobject.c:382 [inline]
 kobject_add+0x13f/0x1b0 lib/kobject.c:426
 device_add+0x3e2/0x17f0 drivers/base/core.c:1879
kobject: 'hci2' (000000009e3c3103): kobject_add_internal:  
parent: 'bluetooth', set: 'devices'
 hci_register_dev+0x3e6/0xb80 net/bluetooth/hci_core.c:3196
kobject: 'hci2' (000000009e3c3103): kobject_uevent_env
 __vhci_create_device+0x2c1/0x580 drivers/bluetooth/hci_vhci.c:139
 vhci_create_device drivers/bluetooth/hci_vhci.c:163 [inline]
 vhci_get_user drivers/bluetooth/hci_vhci.c:219 [inline]
 vhci_write+0x2de/0x470 drivers/bluetooth/hci_vhci.c:299
 call_write_iter include/linux/fs.h:1807 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x6b8/0x9f0 fs/read_write.c:487
kobject: 'hci3' (00000000e8906dbf): fill_kobj_path: path  
= '/devices/virtual/bluetooth/hci3'
kobject: 'hci1' (000000003c3c3740): kobject_uevent_env
 vfs_write+0x1fc/0x560 fs/read_write.c:549
 ksys_write+0x101/0x260 fs/read_write.c:598
kobject: 'hci1' (000000003c3c3740): fill_kobj_path: path  
= '/devices/virtual/bluetooth/hci1'
 __do_sys_write fs/read_write.c:610 [inline]
 __se_sys_write fs/read_write.c:607 [inline]
 __x64_sys_write+0x73/0xb0 fs/read_write.c:607
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
kobject: 'hci6': free name
kobject: 'rfkill160' (000000007e905e9b): kobject_add_internal:  
parent: 'hci3', set: 'devices'
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440e49
Code: e8 ac e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 0b 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffce43766e8 EFLAGS: 00000213 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000440e49
RDX: 0000000000000002 RSI: 00000000200000c0 RDI: 0000000000000003
kobject: 'hci2' (000000009e3c3103): fill_kobj_path: path  
= '/devices/virtual/bluetooth/hci2'
RBP: 0000000000000000 R08: 00000000004002c8 R09: 00000000004002c8
R10: 000000000075f880 R11: 0000000000000213 R12: 000000000000c1e3
R13: 0000000000401d70 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches