WARNING in kernfs_put

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 310c7585e830 Merge tag 'nfsd-4.20' of git://linux-nfs.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1313d999400000
kernel config: https://syzkaller.appspot.com/x/.config?x=13e789936c182ce7
dashboard link: https://syzkaller.appspot.com/bug?extid=f078bc04000fe75f5923
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [gre...@linuxfoundation.org linux-...@vger.kernel.org
t...@kernel.org]

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+f078bc...@syzkaller.appspotmail.com

FAT-fs (loop1): bogus number of reserved sectors
FAT-fs (loop1): Can't find a valid FAT filesystem
------------[ cut here ]------------
kernfs_put: bluetooth/hci0: released with incorrect active_ref 0
WARNING: CPU: 1 PID: 11055 at fs/kernfs/dir.c:527 kernfs_put+0x622/0x760
fs/kernfs/dir.c:525
erofs: read_super, device -> /dev/loop2
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 11055 Comm: syz-executor3 Not tainted 4.19.0+ #312
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+0x244/0x39d lib/dump_stack.c:113
panic+0x238/0x4e7 kernel/panic.c:184
erofs: options ->
noacl,acl,nouser_xattr,fault_injection=0x000000000000a15a,fault_injection=0x0000000000000007,fault_injection=0x0000000000000038,noacl,nouser_xattr,audit,subj_role=ppp0,mask=^MAY_EXEC,smackfshat=selinux,euid=00000000000000000
__warn.cold.8+0x20/0x4a kernel/panic.c:536
report_bug+0x254/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:966
RIP: 0010:kernfs_put+0x622/0x760 fs/kernfs/dir.c:525
Code: 00 49 8b 76 30 48 89 b5 20 ff ff ff e8 57 d9 86 ff 48 8b b5 20 ff ff
ff 44 89 e9 4c 89 fa 48 c7 c7 40 9f 37 88 e8 de 4a 50 ff <0f> 0b e9 ba fb
ff ff e8 52 1c ca ff e9 25 fd ff ff 4c 89 ff e8 45
RSP: 0018:ffff880185bf7868 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff8801c3620000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8165dbd5 RDI: 0000000000000005
RBP: ffff880185bf7970 R08: ffff8801bcd86700 R09: ffffed003b5e5020
R10: ffffed003b5e5020 R11: ffff8801daf28107 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff8801c5f50c40 R15: ffff8801ce2bc280
sysfs_put include/linux/sysfs.h:547 [inline]
kobject_del.part.4+0x42/0xf0 lib/kobject.c:593
kobject_del+0x1f/0x30 lib/kobject.c:588
device_del+0x6f8/0xb70 drivers/base/core.c:2093
hci_unregister_dev+0x3a2/0x990 net/bluetooth/hci_core.c:3355
vhci_release+0x76/0xf0 drivers/bluetooth/hci_vhci.c:354
__fput+0x385/0xa30 fs/file_table.c:278
____fput+0x15/0x20 fs/file_table.c:309
task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
erofs: cannot find valid erofs superblock
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x411021
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 34 19 00 00 c3 48
83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48
89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007fffb3530200 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000411021
RDX: 0000000000000000 RSI: 00000000007303a0 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000730390 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000001 R14: 0000000000000096 R15: 0000000000000003
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Dmitry Vyukov]

On Wed, Oct 31, 2018 at 4:48 PM, syzbot
<syzbot+f078bc...@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 310c7585e830 Merge tag 'nfsd-4.20' of git://linux-nfs.org/..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1313d999400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=13e789936c182ce7
> dashboard link: https://syzkaller.appspot.com/bug?extid=f078bc04000fe75f5923
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> CC: [gre...@linuxfoundation.org linux-...@vger.kernel.org
> t...@kernel.org]
>
> 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+f078bc...@syzkaller.appspotmail.com

Looks like

#syz dup: WARNING in kernfs_get

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