======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.5.9181/27557 is trying to acquire lock:
ffff88810efb7938 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x72a/0xe80

but task is already holding lock:
ffff88803290b080 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&of->mutex){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       kernfs_fop_write_iter+0x1d8/0x540
       iter_file_splice_write+0xa31/0x1240
       do_splice+0xf14/0x1970
       __se_sys_splice+0x353/0x490
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&pipe->mutex){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       anon_pipe_write+0x28f/0x1a30
       __kernel_write_iter+0x44a/0x8f0
       __kernel_write+0x106/0x170
       autofs_notify_daemon+0x73d/0xe80
       autofs_wait+0x11bd/0x1880
       autofs_mount_wait+0x16b/0x390
       autofs_d_automount+0x64e/0x810
       __traverse_mounts+0x2fe/0x5d0
       step_into_slowpath+0x4ba/0x820
       path_lookupat+0x433/0x8c0
       filename_lookup+0x265/0x5d0
       kern_path+0x3d/0x150
       unix_find_other+0x18d/0xb40
       unix_dgram_connect+0x2de/0xba0
       __sys_connect+0x316/0x450
       __x64_sys_connect+0x7a/0x90
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&sbi->pipe_mutex){+.+.}-{4:4}:
       __lock_acquire+0x15ff/0x2e50
       lock_acquire+0x115/0x350
       __mutex_lock+0x19d/0x1550
       autofs_notify_daemon+0x72a/0xe80
       autofs_wait+0x11bd/0x1880
       autofs_mount_wait+0x16b/0x390
       autofs_d_automount+0x64e/0x810
       __traverse_mounts+0x2fe/0x5d0
       step_into_slowpath+0x4ba/0x820
       path_lookupat+0x433/0x8c0
       filename_lookup+0x265/0x5d0
       kern_path+0x3d/0x150
       lookup_bdev+0xc8/0x2b0
       resume_store+0x16f/0x4f0
       kernfs_fop_write_iter+0x3a4/0x540
       vfs_write+0x612/0xba0
       ksys_write+0x150/0x270
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &sbi->pipe_mutex --> &pipe->mutex --> &of->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&of->mutex);
                               lock(&pipe->mutex);
                               lock(&of->mutex);
  lock(&sbi->pipe_mutex);

 *** DEADLOCK ***

locks held by syz.5.9181/27557: 4, last CPU#0:
 #0: ffff88801226a0f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff888175b98460 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffff88803290b080 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540
 #3: ffff888103ec63c8 (kn->active#61){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x22b/0x540

stack backtrace:
CPU: 0 UID: 0 PID: 27557 Comm: syz.5.9181 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
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+0xe8/0x150
 print_circular_bug+0x2e2/0x300
 check_noncircular+0x12f/0x150
 __lock_acquire+0x15ff/0x2e50
 lock_acquire+0x115/0x350
 __mutex_lock+0x19d/0x1550
 autofs_notify_daemon+0x72a/0xe80
 autofs_wait+0x11bd/0x1880
 autofs_mount_wait+0x16b/0x390
 autofs_d_automount+0x64e/0x810
 __traverse_mounts+0x2fe/0x5d0
 step_into_slowpath+0x4ba/0x820
 path_lookupat+0x433/0x8c0
 filename_lookup+0x265/0x5d0
 kern_path+0x3d/0x150
 lookup_bdev+0xc8/0x2b0
 resume_store+0x16f/0x4f0
 kernfs_fop_write_iter+0x3a4/0x540
 vfs_write+0x612/0xba0
 ksys_write+0x150/0x270
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f686719e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6868020028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f6867425fa0 RCX: 00007f686719e159
RDX: 0000000000000012 RSI: 0000200000000040 RDI: 0000000000000008
RBP: 00007f6867235024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6867426038 R14: 00007f6867425fa0 R15: 00007ffc7809b658
 </TASK>
PM: Image not found (code -6)
