======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     Y
------------------------------------------------------
syz.6.1597/11373 is trying to acquire lock:
ffff88805951d2e0 (DCACHE_PAR_LOOKUP){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
ffff88805951d2e0 (DCACHE_PAR_LOOKUP){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
ffff88805951d2e0 (DCACHE_PAR_LOOKUP){+.+.}-{0:0}, at: __d_alloc_parallel+0x39e/0x1700 fs/dcache.c:2881

but task is already holding lock:
ffff888022b10eb8 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
ffff888022b10eb8 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: lookup_slow+0x46/0x80 fs/namei.c:1935

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&type->i_mutex_dir_key#5){++++}-{4:4}:
       down_read+0x45/0x320 kernel/locking/rwsem.c:1574
       inode_lock_shared include/linux/fs.h:1039 [inline]
       lookup_slow+0x46/0x80 fs/namei.c:1935
       ovl_lookup_positive_unlocked fs/overlayfs/namei.c:216 [inline]
       ovl_lookup_single+0x323/0xe90 fs/overlayfs/namei.c:260
       ovl_lookup_layer+0x377/0x440 fs/overlayfs/namei.c:365
       ovl_lookup_layers fs/overlayfs/namei.c:1109 [inline]
       ovl_lookup+0x5e5/0x1c80 fs/overlayfs/namei.c:1403
       __lookup_slow+0x1fb/0x2f0 fs/namei.c:1919
       lookup_slow+0x59/0x80 fs/namei.c:1936
       walk_component fs/namei.c:2282 [inline]
       lookup_last fs/namei.c:2789 [inline]
       path_lookupat+0x3f5/0x8c0 fs/namei.c:2813
       filename_lookup+0x265/0x5d0 fs/namei.c:2842
       __do_sys_chdir fs/open.c:557 [inline]
       __se_sys_chdir+0xa8/0x2a0 fs/open.c:550
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (DCACHE_PAR_LOOKUP){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3209 [inline]
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
       lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
       d_wait_lookup fs/dcache.c:2838 [inline]
       __d_alloc_parallel+0xc32/0x1700 fs/dcache.c:2942
       __lookup_slow+0x82/0x2f0 fs/namei.c:1904
       lookup_slow+0x59/0x80 fs/namei.c:1936
       walk_component fs/namei.c:2282 [inline]
       link_path_walk+0xd22/0x1910 fs/namei.c:2656
       path_lookupat+0xe4/0x8c0 fs/namei.c:2812
       filename_lookup+0x265/0x5d0 fs/namei.c:2842
       user_path_at+0x40/0x160 fs/namei.c:3641
       do_mount fs/namespace.c:4191 [inline]
       __do_sys_mount fs/namespace.c:4407 [inline]
       __se_sys_mount+0x2dc/0x420 fs/namespace.c:4384
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&type->i_mutex_dir_key#5);
                               lock(DCACHE_PAR_LOOKUP);
                               lock(&type->i_mutex_dir_key#5);
  lock(DCACHE_PAR_LOOKUP);

 *** DEADLOCK ***

locks held by syz.6.1597/11373: 1, last CPU#1:
 #0: ffff888022b10eb8 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff888022b10eb8 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: lookup_slow+0x46/0x80 fs/namei.c:1935

stack backtrace:
CPU: 1 UID: 0 PID: 11373 Comm: syz.6.1597 Tainted: G             L     Y syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP, [Y]=FORCED_BIND
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
 check_prev_add kernel/locking/lockdep.c:3209 [inline]
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 d_wait_lookup fs/dcache.c:2838 [inline]
 __d_alloc_parallel+0xc32/0x1700 fs/dcache.c:2942
 __lookup_slow+0x82/0x2f0 fs/namei.c:1904
 lookup_slow+0x59/0x80 fs/namei.c:1936
 walk_component fs/namei.c:2282 [inline]
 link_path_walk+0xd22/0x1910 fs/namei.c:2656
 path_lookupat+0xe4/0x8c0 fs/namei.c:2812
 filename_lookup+0x265/0x5d0 fs/namei.c:2842
 user_path_at+0x40/0x160 fs/namei.c:3641
 do_mount fs/namespace.c:4191 [inline]
 __do_sys_mount fs/namespace.c:4407 [inline]
 __se_sys_mount+0x2dc/0x420 fs/namespace.c:4384
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3e6db9e159
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:00007f3e6e9d0028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f3e6de26090 RCX: 00007f3e6db9e159
RDX: 0000200000000080 RSI: 0000200000000040 RDI: 0000000000000000
RBP: 00007f3e6dc3506b R08: 00002000000000c0 R09: 0000000000000000
R10: 0000000001810080 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3e6de26128 R14: 00007f3e6de26090 R15: 00007ffd45eb2958
 </TASK>