------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#0: ksoftirqd/0/15
WARNING: ./include/linux/ns_common.h:255 at put_user_ns include/linux/user_namespace.h:189 [inline], CPU#0: ksoftirqd/0/15
WARNING: ./include/linux/ns_common.h:255 at delayed_free_pidns+0x118/0x150 kernel/pid_namespace.c:145, CPU#0: ksoftirqd/0/15
Modules linked in:
CPU: 0 UID: 0 PID: 15 Comm: ksoftirqd/0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__ns_ref_put include/linux/ns_common.h:255 [inline]
RIP: 0010:put_user_ns include/linux/user_namespace.h:189 [inline]
RIP: 0010:delayed_free_pidns+0x118/0x150 kernel/pid_namespace.c:145
Code: 85 ed 7e 2b e8 99 9f 03 00 48 83 c3 a8 48 8b 3d 5e be c7 17 48 89 de 5b 41 5c 41 5e 41 5f 5d e9 1e 1e 5f 00 e8 79 9f 03 00 90 <0f> 0b 90 eb b4 e8 6e 9f 03 00 4c 89 ff be 03 00 00 00 e8 01 fb d2
RSP: 0018:ffffc90000147890 EFLAGS: 00010246
RAX: ffffffff81bde0b7 RBX: ffff88806ad4c868 RCX: ffff88801cafbd00
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffff888030c14193 R09: 1ffff11006182832
R10: dffffc0000000000 R11: ffffed1006182833 R12: dffffc0000000000
R13: ffffffff81a903d7 R14: ffff888030c14000 R15: ffff888030c14190
FS:  0000000000000000(0000) GS:ffff888125ec2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6f6fd56000 CR3: 000000002768a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 rcu_do_batch kernel/rcu/tree.c:2605 [inline]
 rcu_core+0xcab/0x1770 kernel/rcu/tree.c:2861
 handle_softirqs+0x286/0x870 kernel/softirq.c:626
 run_ksoftirqd+0x9b/0x100 kernel/softirq.c:1067
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>