------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#1: kworker/1:5/5932
WARNING: ./include/linux/ns_common.h:255 at put_user_ns include/linux/user_namespace.h:189 [inline], CPU#1: kworker/1:5/5932
WARNING: ./include/linux/ns_common.h:255 at delayed_free_pidns+0x118/0x150 kernel/pid_namespace.c:145, CPU#1: kworker/1:5/5932
Modules linked in:
CPU: 1 UID: 0 PID: 5932 Comm: kworker/1:5 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: mld mld_dad_work
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:ffffc90000a08c50 EFLAGS: 00010246
RAX: ffffffff81bde0b7 RBX: ffff8880273605b8 RCX: ffff88802bc18000
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffff888059a94193 R09: 1ffff1100b352832
R10: dffffc0000000000 R11: ffffed100b352833 R12: dffffc0000000000
R13: ffffffff81a903d7 R14: ffff888059a94000 R15: ffff888059a94190
FS:  0000000000000000(0000) GS:ffff888125fc2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3bb64eef98 CR3: 000000000dd36000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 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
 do_softirq+0xec/0x180 kernel/softirq.c:523
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x17d/0x1c0 kernel/softirq.c:450
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 rt6_uncached_list_add net/ipv6/route.c:146 [inline]
 icmp6_dst_alloc+0x3a5/0x420 net/ipv6/route.c:3340
 mld_sendpack+0x683/0xe60 net/ipv6/mcast.c:1844
 mld_dad_work+0x46/0x490 net/ipv6/mcast.c:2294
 process_one_work+0x94a/0x15d0 kernel/workqueue.c:3267
 process_scheduled_works kernel/workqueue.c:3350 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3431
 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>