WARNING in kernfs

WARNING in kernfs_put
Status: upstream: reported C repro on 2019/04/25 06:10
Reported-by: syzbot+ccadabca20bdfa802ef3@syzkaller.appspotmail.com
First crash: 206d, last: 139d

similar bugs (2):
Kernel	Title	Repro	Bisected	Count	Last	Reported	Patched	Status
linux-4.19	WARNING in kernfs_put	C		1	143d	143d	0/1	upstream: reported C repro on 2019/06/27 08:24
upstream	WARNING in kernfs_put	C		4	260d	381d	0/14	closed as dup on 2018/10/31 16:05

Sample crash report:

Bluetooth: Can't register HCI device
kernfs_put: bluetooth/hci1: released with incorrect active_ref 0
------------[ cut here ]------------
WARNING: CPU: 0 PID: 8575 at fs/kernfs/dir.c:525 kernfs_put fs/kernfs/dir.c:525 [inline]
WARNING: CPU: 0 PID: 8575 at fs/kernfs/dir.c:525 kernfs_put.cold+0x8a/0xa4 fs/kernfs/dir.c:506
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 8575 Comm: syz-executor349 Not tainted 4.14.113 #3
kobject: 'hci4' (ffff8880757519e8): fill_kobj_path: path = '/devices/virtual/bluetooth/hci4'
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+0x138/0x19c lib/dump_stack.c:53
 panic+0x1f2/0x438 kernel/panic.c:182
kobject: 'rfkill1309' (ffff88809372a0e8): kobject_add_internal: parent: 'hci4', set: 'devices'
 __warn.cold+0x2f/0x34 kernel/panic.c:546
 report_bug+0x216/0x254 lib/bug.c:186
kobject: 'rfkill1309' (ffff88809372a0e8): kobject_uevent_env
 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
kobject: 'rfkill1309' (ffff88809372a0e8): fill_kobj_path: path = '/devices/virtual/bluetooth/hci4/rfkill1309'
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
kobject: 'rfkill1309' (ffff88809372a0e8): kobject_uevent_env
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:944
RIP: 0010:kernfs_put fs/kernfs/dir.c:525 [inline]
RIP: 0010:kernfs_put.cold+0x8a/0xa4 fs/kernfs/dir.c:506
RSP: 0018:ffff88809805fae0 EFLAGS: 00010286
kobject: 'rfkill1309' (ffff88809372a0e8): fill_kobj_path: path = '/devices/virtual/bluetooth/hci4/rfkill1309'
RAX: 0000000000000040 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffed101300bf52
RBP: ffff88809805fb38 R08: 0000000000000040 R09: 0000000000000000
kobject: 'rfkill1309' (ffff88809372a0e8): kobject_cleanup, parent           (null)
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880a86c6d20
R13: ffff888093b8a540 R14: ffff8880a86c6d50 R15: ffffffff86fa5960
 sysfs_put include/linux/sysfs.h:549 [inline]
 kobject_del.part.0+0x42/0xf0 lib/kobject.c:576
kobject: 'rfkill1309' (ffff88809372a0e8): calling ktype release
 kobject_del+0x20/0x30 lib/kobject.c:571
 device_del+0x68c/0xaa0 drivers/base/core.c:2023
 hci_unregister_dev+0x298/0x7d0 net/bluetooth/hci_core.c:3212
kobject: 'rfkill1309': free name
 vhci_release+0x76/0xf0 drivers/bluetooth/hci_vhci.c:354
 __fput+0x277/0x7a0 fs/file_table.c:210
kobject: 'hci4' (ffff8880757519e8): kobject_uevent_env
 ____fput+0x16/0x20 fs/file_table.c:244
 task_work_run+0x119/0x190 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x7df/0x2c10 kernel/exit.c:874
kobject: 'hci4' (ffff8880757519e8): fill_kobj_path: path = '/devices/virtual/bluetooth/hci4'
kobject: 'bluetooth' (ffff88808a7e2d80): kobject_cleanup, parent           (null)
 do_group_exit+0x111/0x330 kernel/exit.c:977
 SYSC_exit_group kernel/exit.c:988 [inline]
 SyS_exit_group+0x1d/0x20 kernel/exit.c:986
 do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
kobject: 'bluetooth' (ffff88808a7e2d80): calling ktype release
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x43fee8
RSP: 002b:00007ffe396bbc48 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
kobject: 'bluetooth': free name
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043fee8
kobject: 'hci4' (ffff8880757519e8): kobject_cleanup, parent           (null)
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004bf710 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 00000000004002c8 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d1180 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..

Crashes (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	Maintainers
ci2-linux-4-14	2019/04/25 05:09	linux-4.14.y	68d7a45e	8e3c52b1	.config	log	report	syz	C	gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, tj@kernel.org
ci2-linux-4-14	2019/06/30 23:16	linux-4.14.y	f4cc0ed9	699d6448	.config	log	report	syz	C	gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, tj@kernel.org