loop6: detected capacity change from 0 to 4096
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.6.274/8634 is trying to acquire lock:
ffff888129766f28 (&ni->ni_lock/5){+.+.}-{4:4}, at: attr_data_get_block+0x2ec/0x1ec0

but task is already holding lock:
ffff8880233981e0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x211/0x4d0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&mm->mmap_lock){++++}-{4:4}:
       lock_acquire+0x120/0x360
       __might_fault+0xcc/0x130
       _copy_to_user+0x2c/0xb0
       fiemap_fill_next_extent+0x1c0/0x390
       ni_fiemap+0x89c/0xbf0
       ntfs_fiemap+0x11d/0x1a0
       do_vfs_ioctl+0x1173/0x1430
       __se_sys_ioctl+0x82/0x170
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&ni->ni_lock/5){+.+.}-{4:4}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       __mutex_lock+0x187/0x1350
       attr_data_get_block+0x2ec/0x1ec0
       ntfs_file_mmap_prepare+0x4cf/0x7d0
       mmap_region+0xb41/0x20c0
       do_mmap+0xc45/0x10d0
       vm_mmap_pgoff+0x2a6/0x4d0
       ksys_mmap_pgoff+0x51f/0x760
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&mm->mmap_lock);
                               lock(&ni->ni_lock/5);
                               lock(&mm->mmap_lock);
  lock(&ni->ni_lock/5);

 *** DEADLOCK ***

1 lock held by syz.6.274/8634:
 #0: ffff8880233981e0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x211/0x4d0

stack backtrace:
CPU: 1 UID: 0 PID: 8634 Comm: syz.6.274 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_circular_bug+0x2ee/0x310
 check_noncircular+0x134/0x160
 validate_chain+0xb9b/0x2140
 __lock_acquire+0xab9/0xd20
 lock_acquire+0x120/0x360
 __mutex_lock+0x187/0x1350
 attr_data_get_block+0x2ec/0x1ec0
 ntfs_file_mmap_prepare+0x4cf/0x7d0
 mmap_region+0xb41/0x20c0
 do_mmap+0xc45/0x10d0
 vm_mmap_pgoff+0x2a6/0x4d0
 ksys_mmap_pgoff+0x51f/0x760
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7cec38ec29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7ced14a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f7cec5d5fa0 RCX: 00007f7cec38ec29
RDX: 00000000027ffff7 RSI: 0000000000004000 RDI: 0000200000ffc000
RBP: 00007f7cec411e41 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000012 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7cec5d6038 R14: 00007f7cec5d5fa0 R15: 00007ffed3e99cb8
 </TASK>
