==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff8881306db190 by task syz-executor/288

CPU: 1 PID: 288 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <IRQ>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351
 rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
 rcu_do_batch+0x4bc/0xc30 kernel/rcu/tree.c:2285
 rcu_core+0x486/0xf00 kernel/rcu/tree.c:2557
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2574
 handle_softirqs+0x1d7/0x600 kernel/softirq.c:642
 __do_softirq kernel/softirq.c:680 [inline]
 invoke_softirq kernel/softirq.c:497 [inline]
 __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:729
 irq_exit_rcu+0x9/0x10 kernel/softirq.c:741
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:vm_normal_page+0xa/0x200 mm/memory.c:633
Code: 03 4c 89 f7 31 f6 e8 65 a7 07 00 eb d1 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 b8 c1 52 38 b8 55 48 89 e5 41 57 41 56 41 55 <41> 54 53 50 49 89 d6 48 89 f3 49 89 ff e8 a4 9f c6 ff 31 ff 4c 89
RSP: 0018:ffffc90000e47698 EFLAGS: 00000246
RAX: 1ffff11025c4512d RBX: 800000012dfb0007 RCX: ffff88810d3d1440
RDX: 800000012dfb0007 RSI: 00007f69040c0000 RDI: ffff88812e228948
RBP: ffffc90000e476b0 R08: ffffea0004c84ceb R09: 1ffffd400099099d
R10: dffffc0000000000 R11: fffff9400099099e R12: ffff8881305d5338
R13: dffffc0000000000 R14: ffff88812ee0e600 R15: 00000000100400fb
 copy_present_pte mm/memory.c:977 [inline]
 copy_pte_range mm/memory.c:1111 [inline]
 copy_pmd_range mm/memory.c:1197 [inline]
 copy_pud_range mm/memory.c:1234 [inline]
 copy_p4d_range mm/memory.c:1258 [inline]
 copy_page_range+0x102e/0x27f0 mm/memory.c:1356
 dup_mmap kernel/fork.c:778 [inline]
 dup_mm kernel/fork.c:1672 [inline]
 copy_mm+0xf90/0x1ad0 kernel/fork.c:1724
 copy_process+0x12d8/0x3500 kernel/fork.c:2487
 kernel_clone+0x22f/0x7f0 kernel/fork.c:2903
 __do_sys_clone kernel/fork.c:3046 [inline]
 __se_sys_clone kernel/fork.c:3030 [inline]
 __x64_sys_clone+0x193/0x200 kernel/fork.c:3030
 x64_sys_call+0x990/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6904fc6bd2
Code: 89 e7 e8 71 8b f7 ff 45 31 c0 31 d2 31 f6 64 48 8b 04 25 10 00 00 00 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 66 89 c5 85 c0 75 3b 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffff9016630 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffff9016630 RCX: 00007f6904fc6bd2
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffff90167bc R08: 0000000000000000 R09: 0000000000000001
R10: 00005555704a37d0 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000000927c0 R14: 0000000000009dfb R15: 00007ffff9016810
 </TASK>

Allocated by task 680:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:380 [inline]
 __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389
 kasan_kmalloc include/linux/kasan.h:212 [inline]
 __do_kmalloc_node mm/slab_common.c:938 [inline]
 __kmalloc+0xb4/0x1e0 mm/slab_common.c:951
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 l2tp_session_create+0x38/0xbd0 net/l2tp/l2tp_core.c:1614
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771
 __sys_connect_file net/socket.c:2001 [inline]
 __sys_connect+0x3da/0x460 net/socket.c:2018
 __do_sys_connect net/socket.c:2028 [inline]
 __se_sys_connect net/socket.c:2025 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2025
 x64_sys_call+0x88d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 43:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:250
 kasan_slab_free include/linux/kasan.h:178 [inline]
 slab_free_hook mm/slub.c:1750 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776
 slab_free mm/slub.c:3712 [inline]
 __kmem_cache_free+0xb7/0x1b0 mm/slub.c:3728
 kfree+0x6f/0xf0 mm/slab_common.c:990
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193
 l2tp_session_delete+0x3df/0x4d0 net/l2tp/l2tp_core.c:1587
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1233 [inline]
 l2tp_tunnel_del_work+0x199/0x410 net/l2tp/l2tp_core.c:1271
 process_one_work+0x717/0xc30 kernel/workqueue.c:2302
 worker_thread+0xa4d/0x11d0 kernel/workqueue.c:2449
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496
 __call_rcu_common kernel/rcu/tree.c:2807 [inline]
 call_rcu+0xcf/0xf50 kernel/rcu/tree.c:2926
 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:446
 __sock_release net/socket.c:652 [inline]
 sock_close+0xc9/0x220 net/socket.c:1390
 __fput+0x1fd/0x8f0 fs/file_table.c:320
 ____fput+0x15/0x20 fs/file_table.c:348
 task_work_run+0x1e1/0x250 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff8881306db000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff8881306db000, ffff8881306db200)

The buggy address belongs to the physical page:
page:ffffea0004c1b600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1306d8
head:ffffea0004c1b600 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004c1b900 dead000000000002 ffff888100042f00
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 289, tgid 289 (syz-executor), ts 22615050179, free_ts 22614013494
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2673
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2680
 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4587
 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5931
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1967 [inline]
 new_slab+0x98/0x3e0 mm/slub.c:2020
 ___slab_alloc+0x70f/0xb70 mm/slub.c:3177
 __slab_alloc+0x5e/0xa0 mm/slub.c:3263
 slab_alloc_node mm/slub.c:3348 [inline]
 __kmem_cache_alloc_node+0x204/0x2d0 mm/slub.c:3423
 __do_kmalloc_node mm/slab_common.c:937 [inline]
 __kmalloc_node_track_caller+0xa1/0x1e0 mm/slab_common.c:958
 kmalloc_reserve net/core/skbuff.c:449 [inline]
 __alloc_skb+0x226/0x4a0 net/core/skbuff.c:518
 alloc_skb include/linux/skbuff.h:1322 [inline]
 nlmsg_new include/net/netlink.h:987 [inline]
 inet6_netconf_notify_devconf+0x107/0x1c0 net/ipv6/addrconf.c:586
 __addrconf_sysctl_register+0x36e/0x3e0 net/ipv6/addrconf.c:7202
 addrconf_sysctl_register+0x147/0x1a0 net/ipv6/addrconf.c:7239
 ipv6_add_dev+0xbf5/0x1130 net/ipv6/addrconf.c:455
 addrconf_notify+0x6d0/0xe30 net/ipv6/addrconf.c:3621
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1581 [inline]
 free_pcp_prepare mm/page_alloc.c:1655 [inline]
 free_unref_page_prepare+0x81b/0x820 mm/page_alloc.c:3622
 free_unref_page+0x93/0x530 mm/page_alloc.c:3720
 free_the_page mm/page_alloc.c:863 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:6021
 free_pages+0x82/0x90 mm/page_alloc.c:6032
 __stack_depot_save+0x45f/0x490 lib/stackdepot.c:506
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_set_track+0x60/0x70 mm/kasan/common.c:53
 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:380 [inline]
 __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:389
 kasan_kmalloc include/linux/kasan.h:212 [inline]
 __do_kmalloc_node mm/slab_common.c:938 [inline]
 __kmalloc_node_track_caller+0xb1/0x1e0 mm/slab_common.c:958
 kmalloc_reserve net/core/skbuff.c:449 [inline]
 __alloc_skb+0x226/0x4a0 net/core/skbuff.c:518
 alloc_skb include/linux/skbuff.h:1322 [inline]
 alloc_uevent_skb+0x85/0x240 lib/kobject_uevent.c:290
 uevent_net_broadcast_tagged lib/kobject_uevent.c:351 [inline]
 kobject_uevent_net_broadcast+0x1b4/0x5b0 lib/kobject_uevent.c:412
 kobject_uevent_env+0x541/0x720 lib/kobject_uevent.c:608
 kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657
 netdev_queue_add_kobject net/core/net-sysfs.c:1671 [inline]
 netdev_queue_update_kobjects+0x22c/0x470 net/core/net-sysfs.c:1712
 register_queue_kobjects net/core/net-sysfs.c:1773 [inline]
 netdev_register_kobject+0x281/0x330 net/core/net-sysfs.c:2013

Memory state around the buggy address:
 ffff8881306db080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881306db100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881306db180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8881306db200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881306db280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	03 4c 89 f7          	add    -0x9(%rcx,%rcx,4),%ecx
   4:	31 f6                	xor    %esi,%esi
   6:	e8 65 a7 07 00       	call   0x7a770
   b:	eb d1                	jmp    0xffffffde
   d:	0f 1f 00             	nopl   (%rax)
  10:	90                   	nop
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
  16:	90                   	nop
  17:	90                   	nop
  18:	90                   	nop
  19:	90                   	nop
  1a:	90                   	nop
  1b:	b8 c1 52 38 b8       	mov    $0xb83852c1,%eax
  20:	55                   	push   %rbp
  21:	48 89 e5             	mov    %rsp,%rbp
  24:	41 57                	push   %r15
  26:	41 56                	push   %r14
  28:	41 55                	push   %r13
* 2a:	41 54                	push   %r12 <-- trapping instruction
  2c:	53                   	push   %rbx
  2d:	50                   	push   %rax
  2e:	49 89 d6             	mov    %rdx,%r14
  31:	48 89 f3             	mov    %rsi,%rbx
  34:	49 89 ff             	mov    %rdi,%r15
  37:	e8 a4 9f c6 ff       	call   0xffc69fe0
  3c:	31 ff                	xor    %edi,%edi
  3e:	4c                   	rex.WR
  3f:	89                   	.byte 0x89