------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#0: syz.1.350/6888
WARNING: ./include/linux/ns_common.h:255 at put_user_ns include/linux/user_namespace.h:189 [inline], CPU#0: syz.1.350/6888
WARNING: ./include/linux/ns_common.h:255 at delayed_free_pidns+0x118/0x150 kernel/pid_namespace.c:145, CPU#0: syz.1.350/6888
Modules linked in:
CPU: 0 UID: 0 PID: 6888 Comm: syz.1.350 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:ffffc90000007bb0 EFLAGS: 00010246
RAX: ffffffff81bde0b7 RBX: ffff888027249078 RCX: ffff888025101e80
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffff88807f558193 R09: 1ffff1100feab032
R10: dffffc0000000000 R11: ffffed100feab033 R12: dffffc0000000000
R13: ffffffff81a903d7 R14: ffff88807f558000 R15: ffff88807f558190
FS:  00007f19bf0376c0(0000) GS:ffff888125ec2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007dc88000 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 kernel/softirq.c:660 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:727
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:743
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1052
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa8/0x110 kernel/locking/spinlock.c:194
Code: 74 05 e8 6b 75 6a f6 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4f f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> c3 08 32 f6 65 8b 05 4c 10 17 07 85 c0 74 40 48 c7 04 24 0e 36
RSP: 0018:ffffc9011b56f560 EFLAGS: 00000206
RAX: 77a422eacc254100 RBX: 0000000000000a06 RCX: 77a422eacc254100
RDX: 0000000000000006 RSI: ffffffff8d786e5e RDI: 0000000000000001
RBP: ffffc9011b56f5f8 R08: ffffffff8f7da977 R09: 1ffffffff1efb52e
R10: dffffc0000000000 R11: fffffbfff1efb52f R12: dffffc0000000000
R13: 1ffff1100aebcc35 R14: ffff8880575e6140 R15: 1ffff920236adeac
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 __skb_try_recv_datagram+0x17c/0x4d0 net/core/datagram.c:267
 __unix_dgram_recvmsg+0x2d4/0xd60 net/unix/af_unix.c:2581
 sock_recvmsg_nosec+0x186/0x1c0 net/socket.c:1082
 ____sys_recvmsg+0x3aa/0x460 net/socket.c:2852
 ___sys_recvmsg+0x1b5/0x510 net/socket.c:2896
 do_recvmmsg+0x307/0x770 net/socket.c:2991
 __sys_recvmmsg net/socket.c:3065 [inline]
 __do_sys_recvmmsg net/socket.c:3088 [inline]
 __se_sys_recvmmsg net/socket.c:3081 [inline]
 __x64_sys_recvmmsg+0x190/0x240 net/socket.c:3081
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f19be18f6c9
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f19bf037038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f19be3e6090 RCX: 00007f19be18f6c9
RDX: 03fffffffffffeda RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007f19be211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f19be3e6128 R14: 00007f19be3e6090 R15: 00007ffd269f8088
 </TASK>
----------------
Code disassembly (best guess):
   0:	74 05                	je     0x7
   2:	e8 6b 75 6a f6       	call   0xf66a7572
   7:	48 c7 44 24 20 00 00 	movq   $0x0,0x20(%rsp)
   e:	00 00
  10:	9c                   	pushf
  11:	8f 44 24 20          	pop    0x20(%rsp)
  15:	f6 44 24 21 02       	testb  $0x2,0x21(%rsp)
  1a:	75 4f                	jne    0x6b
  1c:	f7 c3 00 02 00 00    	test   $0x200,%ebx
  22:	74 01                	je     0x25
  24:	fb                   	sti
  25:	bf 01 00 00 00       	mov    $0x1,%edi
* 2a:	e8 c3 08 32 f6       	call   0xf63208f2 <-- trapping instruction
  2f:	65 8b 05 4c 10 17 07 	mov    %gs:0x717104c(%rip),%eax        # 0x7171082
  36:	85 c0                	test   %eax,%eax
  38:	74 40                	je     0x7a
  3a:	48                   	rex.W
  3b:	c7                   	.byte 0xc7
  3c:	04 24                	add    $0x24,%al
  3e:	0e                   	(bad)
  3f:	36                   	ss