------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#0: syz-executor/5826
WARNING: ./include/linux/ns_common.h:255 at put_user_ns include/linux/user_namespace.h:189 [inline], CPU#0: syz-executor/5826
WARNING: ./include/linux/ns_common.h:255 at delayed_free_pidns+0x118/0x150 kernel/pid_namespace.c:145, CPU#0: syz-executor/5826
Modules linked in:
CPU: 0 UID: 0 PID: 5826 Comm: syz-executor 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: ffff8880320185b8 RCX: ffff888032eb8000
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffff8880584d4193 R09: 1ffff1100b09a832
R10: dffffc0000000000 R11: ffffed100b09a833 R12: dffffc0000000000
R13: ffffffff81a903d7 R14: ffff8880584d4000 R15: ffff8880584d4190
FS:  000055556d700500(0000) GS:ffff888125ec2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd35c1156c0 CR3: 0000000067e7c000 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:debug_lockdep_rcu_enabled+0x2a/0x40 kernel/rcu/update.c:321
Code: f3 0f 1e fa 31 c0 83 3d 47 72 21 04 00 74 1e 83 3d 4a a1 21 04 00 74 15 65 48 8b 0c 25 08 e0 75 92 31 c0 83 b9 2c 0b 00 00 00 <0f> 94 c0 e9 be e5 02 00 cc cc cc cc cc cc cc cc cc cc cc cc cc cc
RSP: 0018:ffffc90003f9f328 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffffff8234457a RCX: ffff888032eb8000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff8234457a
R10: dffffc0000000000 R11: fffff94000363e21 R12: dffffc0000000000
R13: 0000000000000008 R14: 000000000006c7c4 R15: ffff88813fffa5a0
 rcu_read_unlock_sched include/linux/rcupdate.h:977 [inline]
 pfn_valid+0x32a/0x490 include/linux/mmzone.h:2193
 page_table_check_set+0x25/0x730 mm/page_table_check.c:105
 page_table_check_ptes_set include/linux/page_table_check.h:76 [inline]
 set_ptes include/linux/pgtable.h:292 [inline]
 __copy_present_ptes mm/memory.c:1102 [inline]
 copy_present_ptes mm/memory.c:1181 [inline]
 copy_pte_range mm/memory.c:1304 [inline]
 copy_pmd_range+0x5075/0x7f70 mm/memory.c:1392
 copy_pud_range mm/memory.c:1429 [inline]
 copy_p4d_range mm/memory.c:1453 [inline]
 copy_page_range+0xc14/0x1270 mm/memory.c:1541
 dup_mmap+0xf4c/0x1b10 mm/mmap.c:1831
 dup_mm kernel/fork.c:1488 [inline]
 copy_mm+0x13c/0x4b0 kernel/fork.c:1540
 copy_process+0x1663/0x3930 kernel/fork.c:2180
 kernel_clone+0x21e/0x840 kernel/fork.c:2609
 __do_sys_clone kernel/fork.c:2750 [inline]
 __se_sys_clone kernel/fork.c:2734 [inline]
 __x64_sys_clone+0x18b/0x1e0 kernel/fork.c:2734
 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: 0033:0x7f464a585e13
Code: 1f 84 00 00 00 00 00 64 48 8b 04 25 10 00 00 00 45 31 c0 31 d2 31 f6 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 89 c2 85 c0 75 2c 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffd08587fa8 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f464a585e13
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001
R10: 000055556d7007d0 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000000927c0 R14: 0000000000018820 R15: 00007ffd08588140
 </TASK>
----------------
Code disassembly (best guess):
   0:	f3 0f 1e fa          	endbr64
   4:	31 c0                	xor    %eax,%eax
   6:	83 3d 47 72 21 04 00 	cmpl   $0x0,0x4217247(%rip)        # 0x4217254
   d:	74 1e                	je     0x2d
   f:	83 3d 4a a1 21 04 00 	cmpl   $0x0,0x421a14a(%rip)        # 0x421a160
  16:	74 15                	je     0x2d
  18:	65 48 8b 0c 25 08 e0 	mov    %gs:0xffffffff9275e008,%rcx
  1f:	75 92
  21:	31 c0                	xor    %eax,%eax
  23:	83 b9 2c 0b 00 00 00 	cmpl   $0x0,0xb2c(%rcx)
* 2a:	0f 94 c0             	sete   %al <-- trapping instruction
  2d:	e9 be e5 02 00       	jmp    0x2e5f0
  32:	cc                   	int3
  33:	cc                   	int3
  34:	cc                   	int3
  35:	cc                   	int3
  36:	cc                   	int3
  37:	cc                   	int3
  38:	cc                   	int3
  39:	cc                   	int3
  3a:	cc                   	int3
  3b:	cc                   	int3
  3c:	cc                   	int3
  3d:	cc                   	int3
  3e:	cc                   	int3
  3f:	cc                   	int3