------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#1: +}[@/6022
WARNING: ./include/linux/ns_common.h:255 at put_user_ns include/linux/user_namespace.h:189 [inline], CPU#1: +}[@/6022
WARNING: ./include/linux/ns_common.h:255 at delayed_free_pidns+0x118/0x150 kernel/pid_namespace.c:145, CPU#1: +}[@/6022
Modules linked in:
CPU: 1 UID: 0 PID: 6022 Comm: +}[@ 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:ffffc90000a08bb0 EFLAGS: 00010246
RAX: ffffffff81bde0b7 RBX: ffff888075748868 RCX: ffff88802f76db80
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffff88805708c193 R09: 1ffff1100ae11832
R10: dffffc0000000000 R11: ffffed100ae11833 R12: dffffc0000000000
R13: ffffffff81a903d7 R14: ffff88805708c000 R15: ffff88805708c190
FS:  00007febc6f546c0(0000) GS:ffff888125fc2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f75ae9e1708 CR3: 0000000077d16000 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:__orc_find arch/x86/kernel/unwind_orc.c:109 [inline]
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:-1 [inline]
RIP: 0010:unwind_next_frame+0x348/0x2390 arch/x86/kernel/unwind_orc.c:494
Code: 48 81 fb 50 52 8b 8f 0f 83 48 11 00 00 48 c7 c0 50 52 8b 8f 49 29 c5 48 c7 c6 94 4d 03 90 49 c1 fd 02 4a 8d 14 6d 00 00 00 00 <4c> 01 ea 48 01 d2 48 01 f2 48 bd 00 00 00 00 00 fc ff df 0f 84 37
RSP: 0018:ffffc9000afc7498 EFLAGS: 00000206
RAX: ffffffff8f9a468c RBX: ffffffff8f9a468c RCX: ffffffff8f9a4694
RDX: 000000000000000c RSI: ffffffff9019bbca RDI: ffffffff8bbf4180
RBP: ffffffff8f9a4690 R08: 0000000000000011 R09: ffffffff81740fc5
R10: ffffc9000afc75b8 R11: ffffffff81ad7830 R12: ffffffff82280d8b
R13: 0000000000000006 R14: ffffc9000afc7568 R15: ffffffff8f9a4690
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 unpoison_slab_object mm/kasan/common.c:339 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:365
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4982 [inline]
 kmem_cache_alloc_bulk_noprof+0x4fb/0x650 mm/slub.c:7504
 __io_alloc_req_refill+0x9d/0x340 io_uring/io_uring.c:1023
 io_alloc_req io_uring/io_uring.h:549 [inline]
 io_submit_sqes+0xe68/0x2150 io_uring/io_uring.c:2421
 __do_sys_io_uring_enter io_uring/io_uring.c:3267 [inline]
 __se_sys_io_uring_enter+0x2e0/0x2b80 io_uring/io_uring.c:3206
 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: 0033:0x7febc618f6c9
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:00007febc6f54038 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: ffffffffffffffda RBX: 00007febc63e5fa0 RCX: 00007febc618f6c9
RDX: 000000000000fd5d RSI: 00000000000047fa RDI: 0000000000000003
RBP: 00007febc6211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0200000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007febc63e6038 R14: 00007febc63e5fa0 R15: 00007ffd135f8898
 </TASK>
----------------
Code disassembly (best guess):
   0:	48 81 fb 50 52 8b 8f 	cmp    $0xffffffff8f8b5250,%rbx
   7:	0f 83 48 11 00 00    	jae    0x1155
   d:	48 c7 c0 50 52 8b 8f 	mov    $0xffffffff8f8b5250,%rax
  14:	49 29 c5             	sub    %rax,%r13
  17:	48 c7 c6 94 4d 03 90 	mov    $0xffffffff90034d94,%rsi
  1e:	49 c1 fd 02          	sar    $0x2,%r13
  22:	4a 8d 14 6d 00 00 00 	lea    0x0(,%r13,2),%rdx
  29:	00
* 2a:	4c 01 ea             	add    %r13,%rdx <-- trapping instruction
  2d:	48 01 d2             	add    %rdx,%rdx
  30:	48 01 f2             	add    %rsi,%rdx
  33:	48 bd 00 00 00 00 00 	movabs $0xdffffc0000000000,%rbp
  3a:	fc ff df
  3d:	0f                   	.byte 0xf
  3e:	84 37                	test   %dh,(%rdi)