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SubjectWARNING in kernfs_get

syzbot found the following crash on:

HEAD commit: 9a5682765a2e Merge branch 'x86-urgent-for-linus' of git://..
git tree: upstream
console output:
kernel config:
dashboard link:
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:
C reproducer:

IMPORTANT: if you fix the bug, please add the following tag to the commit:

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'
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..

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