------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#0: udevd/5839
WARNING: ./include/linux/ns_common.h:255 at put_user_ns include/linux/user_namespace.h:189 [inline], CPU#0: udevd/5839
WARNING: ./include/linux/ns_common.h:255 at delayed_free_pidns+0x118/0x150 kernel/pid_namespace.c:145, CPU#0: udevd/5839
Modules linked in:
CPU: 0 UID: 0 PID: 5839 Comm: udevd 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: ffff888020fc8868 RCX: ffff88807c2d8000
RDX: 0000000000000100 RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffff888031fb0193 R09: 1ffff110063f6032
R10: dffffc0000000000 R11: ffffed10063f6033 R12: dffffc0000000000
R13: ffffffff81a903d7 R14: ffff888031fb0000 R15: ffff888031fb0190
FS:  00007f8a79ca8880(0000) GS:ffff888125ec2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000565056b5df20 CR3: 000000005841e000 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:unwind_next_frame+0x117c/0x2390 arch/x86/kernel/unwind_orc.c:641
Code: 0f b6 04 2f 84 c0 0f 85 f9 0f 00 00 c6 03 00 4c 8b 64 24 10 4c 8b 7c 24 28 48 8b 44 24 40 0f b6 04 28 84 c0 0f 85 8a 0d 00 00 <41> 0f b6 04 2f 84 c0 0f 85 a1 0d 00 00 0f b7 32 c1 ee 04 83 e6 0f
RSP: 0018:ffffc900040bf2f8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffc900040bf400 RCX: 0000000000000000
RDX: ffffffff9018e32c RSI: 0000000000000000 RDI: ffffc900040bf428
RBP: dffffc0000000000 R08: ffffc900040bf427 R09: 0000000000000000
R10: ffffc900040bf418 R11: fffff52000817e85 R12: ffffc900040bf7e8
R13: ffffc900040bf418 R14: ffffc900040bf3c8 R15: 1ffffffff2031c65
 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
 poison_kmalloc_redzone mm/kasan/common.c:397 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:414
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __kmalloc_cache_noprof+0x3e2/0x700 mm/slub.c:5775
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 kernfs_fop_open+0x397/0xca0 fs/kernfs/file.c:641
 do_dentry_open+0x953/0x13f0 fs/open.c:962
 vfs_open+0x3b/0x340 fs/open.c:1094
 do_open fs/namei.c:3975 [inline]
 path_openat+0x2efb/0x3860 fs/namei.c:4134
 do_filp_open+0x1fa/0x410 fs/namei.c:4161
 do_sys_openat2+0x121/0x1c0 fs/open.c:1434
 do_sys_open fs/open.c:1449 [inline]
 __do_sys_openat fs/open.c:1465 [inline]
 __se_sys_openat fs/open.c:1460 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1460
 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: 0033:0x7f8a794a7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fffcec2cf90 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f8a79ca8880 RCX: 00007f8a794a7407
RDX: 0000000000080000 RSI: 00007fffcec2d110 RDI: ffffffffffffff9c
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000056504d3f47f5
R13: 000056504d3f47f5 R14: 0000000000000001 R15: 000056504d40f140
 </TASK>
----------------
Code disassembly (best guess):
   0:	0f b6 04 2f          	movzbl (%rdi,%rbp,1),%eax
   4:	84 c0                	test   %al,%al
   6:	0f 85 f9 0f 00 00    	jne    0x1005
   c:	c6 03 00             	movb   $0x0,(%rbx)
   f:	4c 8b 64 24 10       	mov    0x10(%rsp),%r12
  14:	4c 8b 7c 24 28       	mov    0x28(%rsp),%r15
  19:	48 8b 44 24 40       	mov    0x40(%rsp),%rax
  1e:	0f b6 04 28          	movzbl (%rax,%rbp,1),%eax
  22:	84 c0                	test   %al,%al
  24:	0f 85 8a 0d 00 00    	jne    0xdb4
* 2a:	41 0f b6 04 2f       	movzbl (%r15,%rbp,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	0f 85 a1 0d 00 00    	jne    0xdd8
  37:	0f b7 32             	movzwl (%rdx),%esi
  3a:	c1 ee 04             	shr    $0x4,%esi
  3d:	83 e6 0f             	and    $0xf,%esi