======================================================
WARNING: possible circular locking dependency detected
4.19.164-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/21860 is trying to acquire lock:
00000000d96b6934 (&pipe->mutex/1){+.+.}, at: pipe_lock_nested fs/pipe.c:62 [inline]
00000000d96b6934 (&pipe->mutex/1){+.+.}, at: pipe_lock+0x63/0x80 fs/pipe.c:70

but task is already holding lock:
00000000b785a2f7 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2780 [inline]
00000000b785a2f7 (sb_writers#3){.+.+}, at: do_splice fs/splice.c:1153 [inline]
00000000b785a2f7 (sb_writers#3){.+.+}, at: __do_sys_splice fs/splice.c:1428 [inline]
00000000b785a2f7 (sb_writers#3){.+.+}, at: __se_sys_splice+0x11de/0x16d0 fs/splice.c:1408

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (sb_writers#3){.+.+}:
       sb_start_write include/linux/fs.h:1579 [inline]
       mnt_want_write+0x3a/0xb0 fs/namespace.c:360
       ovl_create_object+0x96/0x290 fs/overlayfs/dir.c:600
       lookup_open+0x893/0x1a20 fs/namei.c:3235
       do_last fs/namei.c:3327 [inline]
       path_openat+0x1094/0x2df0 fs/namei.c:3537
       do_filp_open+0x18c/0x3f0 fs/namei.c:3567
       do_sys_open+0x3b3/0x520 fs/open.c:1085
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (&ovl_i_mutex_dir_key[depth]){++++}:
       inode_lock_shared include/linux/fs.h:758 [inline]
       do_last fs/namei.c:3326 [inline]
       path_openat+0x17ec/0x2df0 fs/namei.c:3537
       do_filp_open+0x18c/0x3f0 fs/namei.c:3567
       do_open_execat+0x11d/0x5b0 fs/exec.c:853
       __do_execve_file+0x1a8b/0x2360 fs/exec.c:1770
       do_execveat_common fs/exec.c:1879 [inline]
       do_execve+0x35/0x50 fs/exec.c:1896
       __do_sys_execve fs/exec.c:1977 [inline]
       __se_sys_execve fs/exec.c:1972 [inline]
       __x64_sys_execve+0x7c/0xa0 fs/exec.c:1972
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (&sig->cred_guard_mutex){+.+.}:
       proc_pid_attr_write+0x256/0x650 fs/proc/base.c:2599
       __vfs_write+0xf7/0x770 fs/read_write.c:485
       __kernel_write+0x109/0x370 fs/read_write.c:506
       write_pipe_buf+0x153/0x1f0 fs/splice.c:798
       splice_from_pipe_feed fs/splice.c:503 [inline]
       __splice_from_pipe+0x389/0x800 fs/splice.c:627
       splice_from_pipe fs/splice.c:662 [inline]
       default_file_splice_write+0xd8/0x180 fs/splice.c:810
       do_splice_from fs/splice.c:852 [inline]
       do_splice fs/splice.c:1154 [inline]
       __do_sys_splice fs/splice.c:1428 [inline]
       __se_sys_splice+0xfe7/0x16d0 fs/splice.c:1408
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&pipe->mutex/1){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:925 [inline]
       __mutex_lock+0xd7/0x1260 kernel/locking/mutex.c:1072
       pipe_lock_nested fs/pipe.c:62 [inline]
       pipe_lock+0x63/0x80 fs/pipe.c:70
       iter_file_splice_write+0x183/0xbb0 fs/splice.c:700
       do_splice_from fs/splice.c:852 [inline]
       do_splice fs/splice.c:1154 [inline]
       __do_sys_splice fs/splice.c:1428 [inline]
       __se_sys_splice+0xfe7/0x16d0 fs/splice.c:1408
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
  &pipe->mutex/1 --> &ovl_i_mutex_dir_key[depth] --> sb_writers#3

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_writers#3);
                               lock(&ovl_i_mutex_dir_key[depth]);
                               lock(sb_writers#3);
  lock(&pipe->mutex/1);

 *** DEADLOCK ***

1 lock held by syz-executor.0/21860:
 #0: 00000000b785a2f7 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2780 [inline]
 #0: 00000000b785a2f7 (sb_writers#3){.+.+}, at: do_splice fs/splice.c:1153 [inline]
 #0: 00000000b785a2f7 (sb_writers#3){.+.+}, at: __do_sys_splice fs/splice.c:1428 [inline]
 #0: 00000000b785a2f7 (sb_writers#3){.+.+}, at: __se_sys_splice+0x11de/0x16d0 fs/splice.c:1408

stack backtrace:
CPU: 1 PID: 21860 Comm: syz-executor.0 Not tainted 4.19.164-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2fe lib/dump_stack.c:118
 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1221
 check_prev_add kernel/locking/lockdep.c:1865 [inline]
 check_prevs_add kernel/locking/lockdep.c:1978 [inline]
 validate_chain kernel/locking/lockdep.c:2419 [inline]
 __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3415
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3907
 __mutex_lock_common kernel/locking/mutex.c:925 [inline]
 __mutex_lock+0xd7/0x1260 kernel/locking/mutex.c:1072
 pipe_lock_nested fs/pipe.c:62 [inline]
 pipe_lock+0x63/0x80 fs/pipe.c:70
 iter_file_splice_write+0x183/0xbb0 fs/splice.c:700
 do_splice_from fs/splice.c:852 [inline]
 do_splice fs/splice.c:1154 [inline]
 __do_sys_splice fs/splice.c:1428 [inline]
 __se_sys_splice+0xfe7/0x16d0 fs/splice.c:1408
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45e219
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f8b0cceac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 000000000045e219
RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 000000000119bfd8 R08: 00000000088000cc R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119bf8c
R13: 00007ffece0728af R14: 00007f8b0cceb9c0 R15: 000000000119bf8c
XFS (loop4): unknown mount option [™d–”BY·tÒ%çø^ðjv|].