WARNING in kernfs_new_node

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 1e78030e Merge tag 'mmc-v5.3-rc1' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12aab5cc600000
kernel config: https://syzkaller.appspot.com/x/.config?x=e397351d2615e10
dashboard link: https://syzkaller.appspot.com/bug?extid=499aea72daa2cea73cb7
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=111d80fc600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14d9060c600000

The bug was bisected to:

commit 726e41097920a73e4c7c33385dcc0debb1281e18
Author: Benjamin Herrenschmidt <be...@kernel.crashing.org>
Date: Tue Jul 10 00:29:10 2018 +0000

drivers: core: Remove glue dirs from sysfs earlier

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=138b41ec600000
final crash: https://syzkaller.appspot.com/x/report.txt?x=104b41ec600000
console output: https://syzkaller.appspot.com/x/log.txt?x=178b41ec600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+499aea...@syzkaller.appspotmail.com
Fixes: 726e41097920 ("drivers: core: Remove glue dirs from sysfs earlier")

debugfs: Directory 'hci3' with parent 'bluetooth' already present!
------------[ cut here ]------------
WARNING: CPU: 0 PID: 9903 at fs/kernfs/dir.c:493 kernfs_get
fs/kernfs/dir.c:493 [inline]
WARNING: CPU: 0 PID: 9903 at fs/kernfs/dir.c:493
kernfs_new_node+0x155/0x180 fs/kernfs/dir.c:700
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 9903 Comm: syz-executor126 Not tainted 5.3.0-rc2+ #59
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+0x1d8/0x2f8 lib/dump_stack.c:113
panic+0x29b/0x7d9 kernel/panic.c:219
__warn+0x22f/0x230 kernel/panic.c:576
report_bug+0x190/0x290 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:179 [inline]
do_error_trap+0xd7/0x440 arch/x86/kernel/traps.c:272
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:291
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1026
RIP: 0010:kernfs_get fs/kernfs/dir.c:493 [inline]
RIP: 0010:kernfs_new_node+0x155/0x180 fs/kernfs/dir.c:700
Code: d2 ff 4c 89 23 4c 89 f0 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d c3
e8 69 47 98 ff 48 c7 c7 6d b9 7a 88 31 c0 e8 9e a6 80 ff <0f> 0b eb 8e 44
89 e1 80 e1 07 80 c1 03 38 c1 0f 8c 67 ff ff ff 4c
RSP: 0018:ffff88808d96f6f0 EFLAGS: 00010246
RAX: 0000000000000024 RBX: 0000000000000000 RCX: d31929014df6e300
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffff88808d96f728 R08: ffffffff816068e4 R09: fffffbfff11fbdfd
R10: fffffbfff11fbdfd R11: 0000000000000000 R12: ffff88809377b620
R13: ffff8880982858c0 R14: ffff888095d39460 R15: ffff88821b70d150
kernfs_create_dir_ns+0x44/0x130 fs/kernfs/dir.c:1022
sysfs_create_dir_ns+0x161/0x310 fs/sysfs/dir.c:59
create_dir lib/kobject.c:89 [inline]
kobject_add_internal+0x459/0xd50 lib/kobject.c:255
kobject_add_varg lib/kobject.c:390 [inline]
kobject_add+0x138/0x200 lib/kobject.c:442
device_add+0x508/0x1570 drivers/base/core.c:2065
hci_register_dev+0x331/0x720 net/bluetooth/hci_core.c:3307
__vhci_create_device drivers/bluetooth/hci_vhci.c:124 [inline]
vhci_create_device+0x2f3/0x530 drivers/bluetooth/hci_vhci.c:148
vhci_get_user drivers/bluetooth/hci_vhci.c:204 [inline]
vhci_write+0x3ac/0x440 drivers/bluetooth/hci_vhci.c:284
call_write_iter include/linux/fs.h:1870 [inline]
new_sync_write fs/read_write.c:483 [inline]
__vfs_write+0x617/0x7d0 fs/read_write.c:496
vfs_write+0x275/0x590 fs/read_write.c:558
ksys_write+0x16b/0x2a0 fs/read_write.c:611
__do_sys_write fs/read_write.c:623 [inline]
__se_sys_write fs/read_write.c:620 [inline]
__x64_sys_write+0x7b/0x90 fs/read_write.c:620
do_syscall_64+0xfe/0x140 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441d39
Code: e8 4c 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 db 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd7e3026c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441d39
RDX: 0000000000000002 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffdbb1414ac R09: 00007ffdbb1414ac
R10: 00007ffdbb1414ac R11: 0000000000000246 R12: 0000000000014cb3
R13: 0000000000402a30 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Benjamin Herrenschmidt]

On Mon, 2019-08-05 at 05:38 -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:

A fix for that was submitted recently by Muchun Song <smu...@gmail.com
> and should be queued up by Greg.

Cheers,
Ben.

[syzbot]

syzbot suspects this bug was fixed by commit:

commit 810507fe6fd5ff3de429121adff49523fabb643a
Author: Waiman Long <lon...@redhat.com>
Date: Thu Feb 6 15:24:08 2020 +0000

locking/lockdep: Reuse freed chain_hlocks entries

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=177d726fe00000
start commit: 1e78030e Merge tag 'mmc-v5.3-rc1' of git://git.kernel.org/..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=e397351d2615e10
dashboard link: https://syzkaller.appspot.com/bug?extid=499aea72daa2cea73cb7

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=111d80fc600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14d9060c600000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: locking/lockdep: Reuse freed chain_hlocks entries

[Waiman Long]