======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.9.27610/22106 is trying to acquire lock:
ffff8880282d9b08 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xb7/0xe20

but task is already holding lock:
ffff888028cd7468 (&pipe->mutex){+.+.}-{4:4}, at: splice_file_to_pipe+0x2e/0x440

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&pipe->mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360
       __mutex_lock+0x187/0x1350
       iter_file_splice_write+0x1e0/0x10e0
       do_splice+0xc79/0x1660
       __se_sys_splice+0x2e1/0x460
       do_syscall_64+0xfa/0xfa0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (sb_writers#5){.+.+}-{0:0}:
       lock_acquire+0x120/0x360
       sb_start_write+0x4d/0x1c0
       mnt_want_write+0x41/0x90
       ovl_create_object+0xfc/0x310
       path_openat+0x14f4/0x3830
       do_filp_open+0x1fa/0x410
       do_sys_openat2+0x121/0x1c0
       __x64_sys_creat+0x8f/0xc0
       do_syscall_64+0xfa/0xfa0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}:
       lock_acquire+0x120/0x360
       down_read+0x46/0x2e0
       lookup_slow+0x46/0x70
       walk_component+0x2d2/0x400
       path_lookupat+0x163/0x430
       filename_lookup+0x212/0x570
       kern_path+0x35/0x50
       lookup_bdev+0xc0/0x280
       resume_store+0x169/0x460
       kernfs_fop_write_iter+0x3af/0x540
       vfs_write+0x5c9/0xb30
       ksys_write+0x145/0x250
       do_syscall_64+0xfa/0xfa0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&of->mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360
       __mutex_lock+0x187/0x1350
       kernfs_seq_start+0x5c/0x420
       seq_read_iter+0x3f7/0xe20
       do_iter_readv_writev+0x623/0x8c0
       vfs_readv+0x253/0x850
       __x64_sys_preadv+0x197/0x2a0
       do_syscall_64+0xfa/0xfa0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&p->lock){+.+.}-{4:4}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       __mutex_lock+0x187/0x1350
       seq_read_iter+0xb7/0xe20
       proc_reg_read_iter+0x1b7/0x280
       copy_splice_read+0x5d4/0xa50
       splice_file_to_pipe+0x273/0x440
       do_sendfile+0x475/0x7e0
       __se_sys_sendfile64+0x13e/0x190
       do_syscall_64+0xfa/0xfa0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &p->lock --> sb_writers#5 --> &pipe->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pipe->mutex);
                               lock(sb_writers#5);
                               lock(&pipe->mutex);
  lock(&p->lock);

 *** DEADLOCK ***

1 lock held by syz.9.27610/22106:
 #0: ffff888028cd7468 (&pipe->mutex){+.+.}-{4:4}, at: splice_file_to_pipe+0x2e/0x440

stack backtrace:
CPU: 0 UID: 0 PID: 22106 Comm: syz.9.27610 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
 seq_read_iter+0xb7/0xe20
 proc_reg_read_iter+0x1b7/0x280
 copy_splice_read+0x5d4/0xa50
 splice_file_to_pipe+0x273/0x440
 do_sendfile+0x475/0x7e0
 __se_sys_sendfile64+0x13e/0x190
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f85e7f8eba9
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:00007f85e8ecf038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f85e81d5fa0 RCX: 00007f85e7f8eba9
RDX: 0000000000000000 RSI: 000000000000000a RDI: 0000000000000009
RBP: 00007f85e8011e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000200 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f85e81d6038 R14: 00007f85e81d5fa0 R15: 00007fffaef7d388
 </TASK>
