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.
======================================================
WARNING: possible circular locking dependency detected
4.14.227-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/10182 is trying to acquire lock:
 (sb_writers#3){.+.+}, at: [<ffffffff818da0fa>] sb_start_write include/linux/fs.h:1549 [inline]
 (sb_writers#3){.+.+}, at: [<ffffffff818da0fa>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386

but task is already holding lock:
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
 (&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff8189ced2>] inode_lock include/linux/fs.h:719 [inline]
 (&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff8189ced2>] do_last fs/namei.c:3331 [inline]
 (&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff8189ced2>] path_openat+0xde2/0x2970 fs/namei.c:3569

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&ovl_i_mutex_dir_key[depth]#2){++++}:
       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

-> #0 (sb_writers#3){.+.+}:
       lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
       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
       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

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
overlayfs: filesystem on './bus' not supported as upperdir
  lock(&ovl_i_mutex_dir_key[depth]#2);
                               lock(sb_writers#3);
                               lock(&ovl_i_mutex_dir_key[depth]#2);
  lock(sb_writers#3);

 *** DEADLOCK ***

2 locks held by syz-executor.3/10182:
 #0:  (sb_writers#13){.+.+}, at: [<ffffffff818da0fa>] sb_start_write include/linux/fs.h:1549 [inline]
 #0:  (sb_writers#13){.+.+}, at: [<ffffffff818da0fa>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386
 #1:  (&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff8189ced2>] inode_lock include/linux/fs.h:719 [inline]
 #1:  (&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff8189ced2>] do_last fs/namei.c:3331 [inline]
 #1:  (&ovl_i_mutex_dir_key[depth]#2){++++}, at: [<ffffffff8189ced2>] path_openat+0xde2/0x2970 fs/namei.c:3569

stack backtrace:
overlayfs: fs on '.' does not support file handles, falling back to index=off.
CPU: 1 PID: 10182 Comm: syz-executor.3 Not tainted 4.14.227-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
overlayfs: maximum fs stacking depth exceeded
 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
 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
 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
RIP: 0033:0x466459
RSP: 002b:00007f8529395188 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000466459
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000080
RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffd2b79ee2f R14: 00007f8529395300 R15: 0000000000022000
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: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: failed to resolve './file1': -2
overlayfs: failed to resolve './file1': -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: 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: failed to resolve './file1': -2
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: 'file0' not a directory
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: failed to resolve './file1': -2
overlayfs: failed to resolve './file1': -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: 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: failed to resolve './file1': -2
overlayfs: failed to resolve './file1': -2
overlayfs: failed to resolve './file1': -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: './file0' not a directory
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: failed to resolve './file1': -2
overlayfs: failed to resolve './file1': -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: failed to resolve './file1': -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: failed to resolve './file1': -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: failed to resolve './file1': -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: failed to resolve './file1': -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: failed to resolve './file1': -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.