possible deadlock in iterate_dir

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Jun 15, 2020, 2:16:13 AM6/15/20

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Hello,

syzbot found the following crash on:

HEAD commit: b850307b Linux 4.14.184
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=101beae1100000
kernel config: https://syzkaller.appspot.com/x/.config?x=ddc0f08dd6b981c5
dashboard link: https://syzkaller.appspot.com/bug?extid=a208d87dc07db7e0920f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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+a208d8...@syzkaller.appspotmail.com

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
======================================================
overlayfs: filesystem on './bus' not supported as upperdir
WARNING: possible circular locking dependency detected
4.14.184-syzkaller #0 Not tainted
------------------------------------------------------
overlayfs: failed to resolve './file1': -2
syz-executor.2/19356 is trying to acquire lock:
(&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff818f83f7>] iterate_dir+0x387/0x5e0 fs/readdir.c:43

but task is already holding lock:
(sb_writers#3){.+.+}, at: [<ffffffff8192670a>] sb_start_write include/linux/fs.h:1549 [inline]
(sb_writers#3){.+.+}, at: [<ffffffff8192670a>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (sb_writers#3){.+.+}:
percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline]
percpu_down_read include/linux/percpu-rwsem.h:59 [inline]
__sb_start_write+0x1a1/0x2e0 fs/super.c:1363
sb_start_write include/linux/fs.h:1549 [inline]
mnt_want_write+0x3a/0xb0 fs/namespace.c:386
ovl_do_remove+0x65/0xb00 fs/overlayfs/dir.c:759
vfs_rmdir fs/namei.c:3908 [inline]
vfs_rmdir+0x209/0x400 fs/namei.c:3886
do_rmdir+0x2d1/0x340 fs/namei.c:3968
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #0 (&ovl_i_mutex_dir_key[depth]#2){++++}:
lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
down_write_killable+0x37/0xb0 kernel/locking/rwsem.c:68
iterate_dir+0x387/0x5e0 fs/readdir.c:43
ovl_dir_read fs/overlayfs/readdir.c:306 [inline]
ovl_dir_read_merged+0x2cb/0x440 fs/overlayfs/readdir.c:365
ovl_check_empty_dir+0x6e/0x200 fs/overlayfs/readdir.c:870
ovl_check_empty_and_clear+0x74/0xe0 fs/overlayfs/dir.c:306
ovl_remove_and_whiteout fs/overlayfs/dir.c:647 [inline]
ovl_do_remove+0x563/0xb00 fs/overlayfs/dir.c:775
vfs_rmdir fs/namei.c:3908 [inline]
vfs_rmdir+0x209/0x400 fs/namei.c:3886
do_rmdir+0x2d1/0x340 fs/namei.c:3968
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#3);
lock(&ovl_i_mutex_dir_key[depth]#2);
lock(sb_writers#3);
lock(&ovl_i_mutex_dir_key[depth]#2);

*** DEADLOCK ***

4 locks held by syz-executor.2/19356:
#0: (sb_writers#16){.+.+}, at: [<ffffffff8192670a>] sb_start_write include/linux/fs.h:1549 [inline]
#0: (sb_writers#16){.+.+}, at: [<ffffffff8192670a>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386
#1: (&ovl_i_mutex_dir_key[depth]#3/1){+.+.}, at: [<ffffffff818f004e>] inode_lock_nested include/linux/fs.h:754 [inline]
#1: (&ovl_i_mutex_dir_key[depth]#3/1){+.+.}, at: [<ffffffff818f004e>] do_rmdir+0x1de/0x340 fs/namei.c:3956
#2: (&ovl_i_mutex_dir_key[depth]#3){++++}, at: [<ffffffff818e6ad2>] inode_lock include/linux/fs.h:719 [inline]
#2: (&ovl_i_mutex_dir_key[depth]#3){++++}, at: [<ffffffff818e6ad2>] vfs_rmdir fs/namei.c:3897 [inline]
#2: (&ovl_i_mutex_dir_key[depth]#3){++++}, at: [<ffffffff818e6ad2>] vfs_rmdir+0xd2/0x400 fs/namei.c:3886
#3: (sb_writers#3){.+.+}, at: [<ffffffff8192670a>] sb_start_write include/linux/fs.h:1549 [inline]
#3: (sb_writers#3){.+.+}, at: [<ffffffff8192670a>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386

stack backtrace:
CPU: 1 PID: 19356 Comm: syz-executor.2 Not tainted 4.14.184-syzkaller #0
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+0x1b2/0x283 lib/dump_stack.c:58
print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258
check_prev_add kernel/locking/lockdep.c:1905 [inline]
check_prevs_add kernel/locking/lockdep.c:2022 [inline]
validate_chain kernel/locking/lockdep.c:2464 [inline]
__lock_acquire+0x3057/0x42a0 kernel/locking/lockdep.c:3491
lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
down_write_killable+0x37/0xb0 kernel/locking/rwsem.c:68
iterate_dir+0x387/0x5e0 fs/readdir.c:43
ovl_dir_read fs/overlayfs/readdir.c:306 [inline]
ovl_dir_read_merged+0x2cb/0x440 fs/overlayfs/readdir.c:365
ovl_check_empty_dir+0x6e/0x200 fs/overlayfs/readdir.c:870
ovl_check_empty_and_clear+0x74/0xe0 fs/overlayfs/dir.c:306
ovl_remove_and_whiteout fs/overlayfs/dir.c:647 [inline]
ovl_do_remove+0x563/0xb00 fs/overlayfs/dir.c:775
vfs_rmdir fs/namei.c:3908 [inline]
vfs_rmdir+0x209/0x400 fs/namei.c:3886
do_rmdir+0x2d1/0x340 fs/namei.c:3968
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45ca69
RSP: 002b:00007fa66bbcfc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 00000000004fc3c0 RCX: 000000000045ca69
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000280
RBP: 000000000078bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000008c7 R14: 00000000004cba1d R15: 00007fa66bbd06d4
libceph: mon0 [::6]:6789 socket closed (con state CONNECTING)
overlayfs: unrecognized mount option "./file1" or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
CIFS VFS: Malformed UNC in devname.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "l��EK[ M� ��o�^qz�u ��@W'�E΢~�Z��Aˍ *� �z� � b�r�� /��.-�gjv� u�$�;h��T �q�C��
?
Q�3��+D�sUb@�]�� <" or missing value
overlayfs: unrecognized mount option "upperd " or missing value
libceph: mon0 [::6]:6789 socket closed (con state CONNECTING)
netlink: 8 bytes leftover after parsing attributes in process `syz-executor.2'.
CIFS VFS: Malformed UNC in devname.
overlayfs: unrecognized mount option "l��EK[ M� ��o�^qz�u ��@W'�E΢~�Z��Aˍ *� �z� � b�r�� /��.-�gjv� u�$�;h��T �q�C��
?
Q�3��+D�sUb@�]�� <" or missing value
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: unrecognized mount option "upperd " or missing value
netlink: 8 bytes leftover after parsing attributes in process `syz-executor.2'.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "upperdiruʺ=./bus" or missing value
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "upperdiruʺ=./bus" or missing value
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: unrecognized mount option "./file1" or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
libceph: mon0 [::6]:6789 socket closed (con state CONNECTING)
overlayfs: unrecognized mount option "./file1" or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: failed to resolve './file0': -2
overlayfs: failed to resolve './file0': -2
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "l�weUdir=.:file0;�W/?|��Ag�g�ÜJ�^b� �DF/�E=��_��Z��no C� ��HA D�d�2~ � P� ��R ��3��
�X#:�;�N̉ {n��}�Fy ��v$*] �� t " or missing value
libceph: mon0 [::6]:6789 socket closed (con state CONNECTING)
overlayfs: unrecognized mount option "00000000000000000000003" or missing value
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "00000000000000000000003" or missing value
overlayfs: unrecognized mount option "l�weUdir=.:file0;�W/?|��Ag�g�ÜJ�^b� �DF/�E=��_��Z��no C� ��HA D�d�2~ � P� ��R ��3��
�X#:�;�N̉ {n��}�Fy ��v$*] �� t " or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option " " or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option " " or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
libceph: mon0 [::6]:6789 socket closed (con state CONNECTING)
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor.1'.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "./file1" or missing value
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: failed to resolve 'file0�ED-*�~�GD-�=� �*N5�k� v� ��J cB�= � ': -2
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir
libceph: mon0 [::6]:6789 socket closed (con state CONNECTING)
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: failed to resolve 'file0�ED-*�~�GD-�=� �*N5�k� v� ��J cB�= � ': -2
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
libceph: mon0 [::6]:6789 socket closed (con state CONNECTING)
overlayfs: unrecognized mount option "6��z D� '�Q�" or missing value
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "6��z D� '�Q�" or missing value
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "workdirz��;ile1" or missing value
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: unrecognized mount option "workdirz��;ile1" or missing value
overlayfs: unrecognized mount option "lnwerdiz=.|�:�il3�9 J��i3��ևjo�#?�n� >H�[�.��ό��Cr $]�X��B�
%�@1](VJٚ��h" or missing value
hfs: gid requires an argument
hfs: unable to parse mount options
overlayfs: unrecognized mount option "lnwerdiz=.|�:�il3�9 J��i3��ևjo�#?�n� >H�[�.��ό��Cr $]�X��B�
%�@1](VJٚ��h" or missing value
overlayfs: unrecognized mount option "lnwerdiz=.|�:�il3�9 J��i3��ևjo�#?�n� >H�[�.��ό��Cr $]�X��B�
%�@1](VJٚ��h" or missing value
hfs: gid requires an argument
hfs: unable to parse mount options
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "lnwerdiz=.|�:�il3�9 J��i3��ևjo�#?�n� >H�[�.��ό��Cr $]�X��B�
%�@1](VJٚ��h" or missing value
overlayfs: failed to resolve './file0��(.��f=z D� '�Q�': -2
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: failed to resolve './file0��(.��f=z D� '�Q�': -2
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "low " or missing value
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
8021q: adding VLAN 0 to HW filter on device bond0
overlayfs: unrecognized mount option "low " or missing value
overlayfs: unrecognized mount option "0 " or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: failed to resolve 'file0-��JO� 7�بu�܂�+�x�_Z�;� U�ꝱg� � �
Yצ{|} ��زV�"H�': -2
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: failed to resolve 'file0-��JO� 7�بu�܂�+�x�_Z�;� U�ꝱg� � �
Yצ{|} ��زV�"H�': -2
overlayfs: filesystem on './bus' not supported as upperdir
libceph: mon0 [::6]:6789 socket closed (con state CONNECTING)
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "0 " or missing value
overlayfs: unrecognized mount option "loD<rdir=.:file0" or missing value
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "./file1" or missing value
overlayfs: unrecognized mount option "loD<rdir=.:file0" or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "./file1" or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "./file1" or missing value
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot

unread,

Aug 14, 2020, 11:16:16 AM8/14/20

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following issue on:

HEAD commit: 14b58326 Linux 4.14.193
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1130d116900000
kernel config: https://syzkaller.appspot.com/x/.config?x=68ef0287ccbc3b42
dashboard link: https://syzkaller.appspot.com/bug?extid=a208d87dc07db7e0920f
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17449b6e900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a208d8...@syzkaller.appspotmail.com

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

======================================================

WARNING: possible circular locking dependency detected

4.14.193-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.1/8340 is trying to acquire lock:
(&ovl_i_mutex_dir_key[depth]){++++}, at: [<ffffffff81914b37>] iterate_dir+0x387/0x5e0 fs/readdir.c:43

but task is already holding lock:

(sb_writers#3){.+.+}, at: [<ffffffff819441aa>] sb_start_write include/linux/fs.h:1549 [inline]
(sb_writers#3){.+.+}, at: [<ffffffff819441aa>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (sb_writers#3){.+.+}:
percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline]
percpu_down_read include/linux/percpu-rwsem.h:59 [inline]

__sb_start_write+0x19a/0x2e0 fs/super.c:1363

sb_start_write include/linux/fs.h:1549 [inline]
mnt_want_write+0x3a/0xb0 fs/namespace.c:386

ovl_create_object+0x75/0x1d0 fs/overlayfs/dir.c:538
lookup_open+0x77a/0x1750 fs/namei.c:3241
do_last fs/namei.c:3334 [inline]
path_openat+0xe08/0x2970 fs/namei.c:3569
do_filp_open+0x179/0x3c0 fs/namei.c:3603
do_sys_open+0x296/0x410 fs/open.c:1081
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

overlayfs: filesystem on './bus' not supported as upperdir

-> #0 (&ovl_i_mutex_dir_key[depth]){++++}:

lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
down_write_killable+0x37/0xb0 kernel/locking/rwsem.c:68
iterate_dir+0x387/0x5e0 fs/readdir.c:43
ovl_dir_read fs/overlayfs/readdir.c:306 [inline]

ovl_dir_read_merged+0x2c5/0x430 fs/overlayfs/readdir.c:365
overlayfs: 'file0' not a directory
ovl_check_empty_dir+0x6e/0x200 fs/overlayfs/readdir.c:870
ovl_check_empty_and_clear+0x72/0xe0 fs/overlayfs/dir.c:306
ovl_remove_and_whiteout fs/overlayfs/dir.c:647 [inline]
ovl_do_remove+0x563/0xaf0 fs/overlayfs/dir.c:775
vfs_rmdir.part.0+0x144/0x390 fs/namei.c:3908
vfs_rmdir fs/namei.c:3893 [inline]
do_rmdir+0x334/0x3c0 fs/namei.c:3968

do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#3);

lock(&ovl_i_mutex_dir_key[depth]);
lock(sb_writers#3);
lock(&ovl_i_mutex_dir_key[depth]);

*** DEADLOCK ***

4 locks held by syz-executor.1/8340:
#0: (sb_writers#16){.+.+}, at: [<ffffffff819441aa>] sb_start_write include/linux/fs.h:1549 [inline]
#0: (sb_writers#16){.+.+}, at: [<ffffffff819441aa>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386
#1: (&ovl_i_mutex_dir_key[depth]#2/1){+.+.}, at: [<ffffffff8190c09e>] inode_lock_nested include/linux/fs.h:754 [inline]
#1: (&ovl_i_mutex_dir_key[depth]#2/1){+.+.}, at: [<ffffffff8190c09e>] do_rmdir+0x1de/0x3c0 fs/namei.c:3956
#2:
overlayfs: filesystem on './file1' not supported as upperdir
(&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff818f6d8c>] inode_lock include/linux/fs.h:719 [inline]
(&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff818f6d8c>] vfs_rmdir.part.0+0x5c/0x390 fs/namei.c:3897
#3: (sb_writers#3){.+.+}, at: [<ffffffff819441aa>] sb_start_write include/linux/fs.h:1549 [inline]
#3: (sb_writers#3){.+.+}, at: [<ffffffff819441aa>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386

stack backtrace:
CPU: 0 PID: 8340 Comm: syz-executor.1 Not tainted 4.14.193-syzkaller #0

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+0x1b2/0x283 lib/dump_stack.c:58

print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1258

check_prev_add kernel/locking/lockdep.c:1905 [inline]
check_prevs_add kernel/locking/lockdep.c:2022 [inline]
validate_chain kernel/locking/lockdep.c:2464 [inline]

__lock_acquire+0x2e0e/0x3f20 kernel/locking/lockdep.c:3491

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir
lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998

overlayfs: filesystem on './bus' not supported as upperdir

down_write_killable+0x37/0xb0 kernel/locking/rwsem.c:68
iterate_dir+0x387/0x5e0 fs/readdir.c:43

overlayfs: filesystem on './bus' not supported as upperdir

ovl_dir_read fs/overlayfs/readdir.c:306 [inline]
ovl_dir_read_merged+0x2c5/0x430 fs/overlayfs/readdir.c:365

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory
ovl_check_empty_dir+0x6e/0x200 fs/overlayfs/readdir.c:870
overlayfs: 'file0' not a directory
ovl_check_empty_and_clear+0x72/0xe0 fs/overlayfs/dir.c:306
ovl_remove_and_whiteout fs/overlayfs/dir.c:647 [inline]
ovl_do_remove+0x563/0xaf0 fs/overlayfs/dir.c:775
vfs_rmdir.part.0+0x144/0x390 fs/namei.c:3908
vfs_rmdir fs/namei.c:3893 [inline]
do_rmdir+0x334/0x3c0 fs/namei.c:3968
overlayfs: filesystem on './file1' not supported as upperdir
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

overlayfs: fs on '.' does not support file handles, falling back to index=off.

RIP: 0033:0x45d239
RSP: 002b:00007f4aeb2afc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 00000000000260c0 RCX: 000000000045d239
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000580
RBP: 000000000118d0b0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118d08c
R13: 00007fffaafcb6bf R14: 00007f4aeb2b09c0 R15: 000000000118d08c

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir
kauditd_printk_skb: 125 callbacks suppressed
audit: type=1800 audit(1597416957.247:225): pid=8383 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.2" name="file0" dev="sda1" ino=16016 res=0

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: failed to resolve 'file0': -2

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
audit: type=1800 audit(1597416957.297:226): pid=8372 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.0" name="file0" dev="sda1" ino=16038 res=0
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

audit: type=1800 audit(1597416957.297:227): pid=8374 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.5" name="file0" dev="sda1" ino=16055 res=0

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

audit: type=1800 audit(1597416957.307:228): pid=8390 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.4" name="file0" dev="sda1" ino=16074 res=0

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: failed to resolve 'file0': -2

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: failed to resolve 'file0': -2

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

audit: type=1800 audit(1597416957.427:229): pid=8397 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.4" name="file0" dev="sda1" ino=15806 res=0
overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.

audit: type=1800 audit(1597416957.427:230): pid=8398 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.3" name="file0" dev="sda1" ino=15894 res=0

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: 'file0' not a directory
audit: type=1800 audit(1597416957.437:231): pid=8405 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.0" name="file0" dev="sda1" ino=16044 res=0
overlayfs: 'file0' not a directory

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

audit: type=1800 audit(1597416957.477:232): pid=8403 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.1" name="file0" dev="sda1" ino=15750 res=0

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

audit: type=1800 audit(1597416957.567:233): pid=8414 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.5" name="file0" dev="sda1" ino=16051 res=0

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

audit: type=1800 audit(1597416957.577:234): pid=8407 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op="collect_data" cause="failed(directio)" comm="syz-executor.0" name="file0" dev="sda1" ino=16055 res=0

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: 'file0' not a directory
overlayfs: 'file0' not a directory
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: 'file0' not a directory

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory
overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir
overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: failed to resolve 'file0': -2

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './file1' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: 'file0' not a directory

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: 'file0' not a directory

syzbot

unread,

May 11, 2021, 6:44:16 PM5/11/21

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following issue on:

HEAD commit: 7d7d1c0a Linux 4.14.232
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=161c1c23d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=17ee8a0e183900d8
dashboard link: https://syzkaller.appspot.com/bug?extid=a208d87dc07db7e0920f
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13ac118bd00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=175e3263d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a208d8...@syzkaller.appspotmail.com

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

======================================================

WARNING: possible circular locking dependency detected

4.14.232-syzkaller #0 Not tainted

overlayfs: fs on './file0' does not support file handles, falling back to index=off.

------------------------------------------------------
syz-executor372/8005 is trying to acquire lock:
(&ovl_i_mutex_dir_key[depth]){++++}, at: [<ffffffff818ad2f7>] iterate_dir+0x387/0x5e0 fs/readdir.c:43

but task is already holding lock:

overlayfs: fs on '.' does not support file handles, falling back to index=off.

(sb_writers#3){.+.+}, at: [<ffffffff818dc80a>] sb_start_write include/linux/fs.h:1549 [inline]
(sb_writers#3){.+.+}, at: [<ffffffff818dc80a>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

overlayfs: maximum fs stacking depth exceeded

-> #1 (sb_writers#3){.+.+}:
percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline]
percpu_down_read include/linux/percpu-rwsem.h:59 [inline]

__sb_start_write+0x64/0x260 fs/super.c:1342

sb_start_write include/linux/fs.h:1549 [inline]
mnt_want_write+0x3a/0xb0 fs/namespace.c:386

overlayfs: filesystem on './bus' not supported as upperdir

do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #0 (&ovl_i_mutex_dir_key[depth]){++++}:

lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
down_write_killable+0x37/0xb0 kernel/locking/rwsem.c:68
iterate_dir+0x387/0x5e0 fs/readdir.c:43
ovl_dir_read fs/overlayfs/readdir.c:306 [inline]

lock(&ovl_i_mutex_dir_key[depth]);
lock(sb_writers#3);
lock(&ovl_i_mutex_dir_key[depth]);

*** DEADLOCK ***

6 locks held by syz-executor372/8005:
#0: (sb_writers#10){.+.+}, at: [<ffffffff818dc80a>] sb_start_write include/linux/fs.h:1549 [inline]
#0: (sb_writers#10){.+.+}, at: [<ffffffff818dc80a>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386
#1: (&type->s_vfs_rename_key#2){+.+.}, at: [<ffffffff8188e054>] lock_rename+0x54/0x280 fs/namei.c:2889
#2: (&ovl_i_mutex_dir_key[depth]#2/1){+.+.}, at: [<ffffffff8188e0a0>] inode_lock_nested include/linux/fs.h:754 [inline]
#2: (&ovl_i_mutex_dir_key[depth]#2/1){+.+.}, at: [<ffffffff8188e0a0>] lock_rename+0xa0/0x280 fs/namei.c:2893
#3: (&ovl_i_mutex_dir_key[depth]#2/2){+.+.}, at: [<ffffffff8188e0d4>] inode_lock_nested include/linux/fs.h:754 [inline]
#3: (&ovl_i_mutex_dir_key[depth]#2/2){+.+.}, at: [<ffffffff8188e0d4>] lock_rename+0xd4/0x280 fs/namei.c:2894
#4: (&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff818a1c28>] inode_lock include/linux/fs.h:719 [inline]
#4: (&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff818a1c28>] vfs_rename+0xbd8/0x1820 fs/namei.c:4470
#5: (sb_writers#3){.+.+}, at: [<ffffffff818dc80a>] sb_start_write include/linux/fs.h:1549 [inline]
#5: (sb_writers#3){.+.+}, at: [<ffffffff818dc80a>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386

stack backtrace:
CPU: 0 PID: 8005 Comm: syz-executor372 Not tainted 4.14.232-syzkaller #0

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+0x1b2/0x281 lib/dump_stack.c:58
print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1258

check_prev_add kernel/locking/lockdep.c:1905 [inline]
check_prevs_add kernel/locking/lockdep.c:2022 [inline]
validate_chain kernel/locking/lockdep.c:2464 [inline]

__lock_acquire+0x2e0e/0x3f20 kernel/locking/lockdep.c:3491

lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
down_write_killable+0x37/0xb0 kernel/locking/rwsem.c:68
iterate_dir+0x387/0x5e0 fs/readdir.c:43
ovl_dir_read fs/overlayfs/readdir.c:306 [inline]

ovl_dir_read_merged+0x2c5/0x430 fs/overlayfs/readdir.c:365
ovl_check_empty_dir+0x6e/0x200 fs/overlayfs/readdir.c:870
ovl_check_empty_and_clear+0x72/0xe0 fs/overlayfs/dir.c:306
ovl_rename+0x57d/0xf10 fs/overlayfs/dir.c:959
vfs_rename+0x560/0x1820 fs/namei.c:4496
SYSC_renameat2 fs/namei.c:4644 [inline]
SyS_renameat2+0x95b/0xad0 fs/namei.c:4533
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x4462b9
RSP: 002b:00007f1dd13982f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00000000004cb4f0 RCX: 00000000004462b9
RDX: 00000000004462b9 RSI: 0000000020000440 RDI: 0000000020000380
RBP: 000000000049b06c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 0079616c7265766f R14: 69662f7375622f2e R15: 00000000004cb4f8

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: maximum fs stacking depth exceeded

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: maximum fs stacking depth exceeded
overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: maximum fs stacking depth exceeded
overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: maximum fs stacking depth exceeded

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir

overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: maximum fs stacking depth exceeded
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.

overlayfs: fs on '.' does not support file handles, falling back to index=off.
overlayfs: fs on '.' does not support file handles, falling back to index=off.

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.

overlayfs: maximum fs stacking depth exceeded
overlayfs: filesystem on './bus' not supported as upperdir
overlayfs: maximum fs stacking depth exceeded