------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#1: kworker/u8:3/50
WARNING: ./include/linux/ns_common.h:255 at put_user_ns include/linux/user_namespace.h:189 [inline], CPU#1: kworker/u8:3/50
WARNING: ./include/linux/ns_common.h:255 at put_cred_rcu+0x2c5/0x340 kernel/cred.c:61, CPU#1: kworker/u8:3/50
Modules linked in:
CPU: 1 UID: 0 PID: 50 Comm: kworker/u8:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: bat_events batadv_mcast_mla_update
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:put_cred_rcu+0x2c5/0x340 kernel/cred.c:61
Code: 5c 41 5d 41 5e 41 5f 5d e9 78 8c 8d 00 e8 03 8c 32 00 4c 89 e7 be 03 00 00 00 e8 b6 d6 08 03 e9 b8 fe ff ff e8 ec 8b 32 00 90 <0f> 0b 90 eb 9f e8 e1 8b 32 00 4c 89 ff be 03 00 00 00 e8 94 d6 08
RSP: 0018:ffffc90000a08ba8 EFLAGS: 00010246
RAX: ffffffff818ed124 RBX: ffff88802d2d39a0 RCX: ffff88801fee8000
RDX: 0000000000000100 RSI: 0000000000000004 RDI: 0000000000000000
RBP: 0000000000000004 R08: ffff88805d9bc193 R09: 1ffff1100bb37832
R10: dffffc0000000000 R11: ffffed100bb37833 R12: dffffc0000000000
R13: ffff88802d2d3900 R14: ffff88805d9bc000 R15: ffff88805d9bc190
FS:  0000000000000000(0000) GS:ffff888125b83000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2e8a168990 CR3: 0000000065d08000 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:1055 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1055
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:unwind_next_frame+0x19b8/0x2390 arch/x86/kernel/unwind_orc.c:680
Code: 48 c7 c2 40 71 88 8b e8 76 35 2a 00 48 c7 c7 60 d8 33 8e 4c 89 fe e8 57 1b 2a 00 e8 92 ec 33 00 89 d8 48 81 c4 98 00 00 00 5b <41> 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 4c 8b 7c 24 48 eb 89
RSP: 0018:ffffc90000bb7438 EFLAGS: 00000296
RAX: 00000000905c2e01 RBX: ffffc90000bb7520 RCX: cdfc38bffdd95700
RDX: 0000000000000002 RSI: ffffffff8dc71a48 RDI: ffff88801fee8000
RBP: dffffc0000000000 R08: ffffc90000bb77e0 R09: 0000000000000000
R10: ffffc90000bb74b8 R11: fffff52000176e99 R12: ffffc90000bb77f0
R13: ffffc90000bb0000 R14: ffffc90000bb7468 R15: ffffffff81740fc5
 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
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2546 [inline]
 slab_free mm/slub.c:6678 [inline]
 kfree+0x19a/0x6e0 mm/slub.c:6886
 batadv_mcast_mla_list_free net/batman-adv/multicast.c:667 [inline]
 __batadv_mcast_mla_update net/batman-adv/multicast.c:924 [inline]
 batadv_mcast_mla_update+0x3362/0x3600 net/batman-adv/multicast.c:946
 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>
----------------
Code disassembly (best guess):
   0:	48 c7 c2 40 71 88 8b 	mov    $0xffffffff8b887140,%rdx
   7:	e8 76 35 2a 00       	call   0x2a3582
   c:	48 c7 c7 60 d8 33 8e 	mov    $0xffffffff8e33d860,%rdi
  13:	4c 89 fe             	mov    %r15,%rsi
  16:	e8 57 1b 2a 00       	call   0x2a1b72
  1b:	e8 92 ec 33 00       	call   0x33ecb2
  20:	89 d8                	mov    %ebx,%eax
  22:	48 81 c4 98 00 00 00 	add    $0x98,%rsp
  29:	5b                   	pop    %rbx
* 2a:	41 5c                	pop    %r12 <-- trapping instruction
  2c:	41 5d                	pop    %r13
  2e:	41 5e                	pop    %r14
  30:	41 5f                	pop    %r15
  32:	5d                   	pop    %rbp
  33:	c3                   	ret
  34:	cc                   	int3
  35:	cc                   	int3
  36:	cc                   	int3
  37:	cc                   	int3
  38:	cc                   	int3
  39:	4c 8b 7c 24 48       	mov    0x48(%rsp),%r15
  3e:	eb 89                	jmp    0xffffffc9