R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffdab749a5f R14: 00007fead6a2c300 R15: 0000000000022000
 </TASK>
============================================
WARNING: possible recursive locking detected
6.19.0-rc5-next-20260116 #1 Not tainted
--------------------------------------------
syz-executor.4/5344 is trying to acquire lock:
ffffffff85f24e30 (namespace_sem){++++}-{4:4}, at: put_mnt_ns+0xa9/0x170

but task is already holding lock:
ffffffff85f24e30 (namespace_sem){++++}-{4:4}, at: lock_mount_exact+0x7c/0x5e0

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(namespace_sem);
  lock(namespace_sem);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz-executor.4/5344:
 #0: ffff888009448148 (&sb->s_type->i_mutex_key){++++}-{4:4}, at: lock_mount_exact+0x70/0x5e0
 #1: ffffffff85f24e30 (namespace_sem){++++}-{4:4}, at: lock_mount_exact+0x7c/0x5e0

stack backtrace:
CPU: 0 UID: 0 PID: 5344 Comm: syz-executor.4 Not tainted 6.19.0-rc5-next-20260116 #1 PREEMPT(lazy) 
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xca/0x120
 print_deadlock_bug+0x283/0x3c0
 check_deadlock+0x134/0x230
 __lock_acquire+0x10d5/0x2250
 lock_acquire+0x15e/0x2d0
 down_write+0x91/0x1f0
 put_mnt_ns+0xa9/0x170
 path_from_stashed+0x4b3/0x660
 open_namespace_file+0x8d/0x140
 vfs_open_tree+0x4b2/0x1410
 __x64_sys_open_tree+0xa8/0x190
 do_syscall_64+0xbf/0x420
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fead94b6b19
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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fead6a2c188 EFLAGS: 00000246 ORIG_RAX: 00000000000001ac
RAX: ffffffffffffffda RBX: 00007fead95c9f60 RCX: 00007fead94b6b19
RDX: 0000000000088102 RSI: 0000000020000200 RDI: ffffffffffffff9c
RBP: 00007fead6a2c1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffdab749a5f R14: 00007fead6a2c300 R15: 0000000000022000
 </TASK>
netlink: 4 bytes leftover after parsing attributes in process `syz-executor.2'.
netlink: 6 bytes leftover after parsing attributes in process `syz-executor.2'.