==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff8881319cdd90 by task syz-executor/2637

CPU: 1 PID: 2637 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
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+0x1dd/0x5f0 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:memset_erms+0xb/0x10 arch/x86/lib/memset_64.S:65
Code: 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 f3 aa <4c> 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 01 01 01
RSP: 0018:ffffc90003b06338 EFLAGS: 00000202
RAX: ffff88811d2ea800 RBX: 0000000000000060 RCX: 0000000000000000
RDX: 0000000000000060 RSI: 0000000000000000 RDI: ffffc90003b06428
RBP: ffffc90003b06358 R08: ffffc90003b06427 R09: ffffc90003b063c8
R10: dffffc0000000000 R11: fffff52000760c85 R12: 0000000000000000
R13: 1ffff11023a5d5c5 R14: 0000000000000000 R15: ffffc90003b063c8
 __unwind_start+0x34/0x3a0 arch/x86/kernel/unwind_frame.c:378
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xe4/0x150 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
 save_stack+0x121/0x230 mm/page_owner.c:147
 __set_page_owner+0x1f/0x60 mm/page_owner.c:210
 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]
 slab_alloc mm/slub.c:3392 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3399 [inline]
 kmem_cache_alloc+0x1a8/0x320 mm/slub.c:3408
 kmem_cache_zalloc include/linux/slab.h:689 [inline]
 __kernfs_new_node+0xe1/0x670 fs/kernfs/dir.c:616
 kernfs_new_node+0x150/0x260 fs/kernfs/dir.c:692
 __kernfs_create_file+0x4e/0x270 fs/kernfs/file.c:1068
 sysfs_add_file_mode_ns+0x1ce/0x270 fs/sysfs/file.c:294
 create_files fs/sysfs/group.c:76 [inline]
 internal_create_group+0x6b7/0xeb0 fs/sysfs/group.c:176
 sysfs_create_group+0x1f/0x30 fs/sysfs/group.c:202
 netdev_queue_add_kobject net/core/net-sysfs.c:1666 [inline]
 netdev_queue_update_kobjects+0x213/0x470 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
 register_netdevice+0xec9/0x1550 net/core/dev.c:10207
 ip6gre_newlink_common+0x3a3/0x540 net/ipv6/ip6_gre.c:2033
 ip6gre_newlink+0x194/0x7a0 net/ipv6/ip6_gre.c:2064
 rtnl_newlink_create net/core/rtnetlink.c:3434 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3654 [inline]
 rtnl_newlink+0x14dc/0x20d0 net/core/rtnetlink.c:3667
 rtnetlink_rcv_msg+0xb28/0xde0 net/core/rtnetlink.c:6162
 netlink_rcv_skb+0x200/0x450 net/netlink/af_netlink.c:2526
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6180
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x8c1/0xa60 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x8b9/0xbd0 net/netlink/af_netlink.c:1878
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 __sys_sendto+0x4ac/0x660 net/socket.c:2143
 __do_sys_sendto net/socket.c:2155 [inline]
 __se_sys_sendto net/socket.c:2151 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2151
 x64_sys_call+0x83/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
 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: 0033:0x7f6499b5a6d7
Code: 48 89 fa 4c 89 df e8 a8 56 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:00007ffc98b90050 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000555573013500 RCX: 00007f6499b5a6d7
RDX: 0000000000000054 RSI: 00007f649a954670 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007ffc98b900b4 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f649a954670 R15: 0000000000000000
 </TASK>

Allocated by task 2624:
 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 1799:
 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
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0xb0d/0x29f0 kernel/exit.c:896
 __do_sys_exit kernel/exit.c:1006 [inline]
 __se_sys_exit kernel/exit.c:1004 [inline]
 __cfi___ia32_sys_exit+0x0/0x10 kernel/exit.c:1004
 x64_sys_call+0x67/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:61
 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

Second to 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
 fib6_info_release include/net/ip6_fib.h:350 [inline]
 __ip6_del_rt+0xf5/0x150 net/ipv6/route.c:3922
 ip6_del_rt+0xbe/0x110 net/ipv6/route.c:3933
 __ipv6_ifa_notify+0x877/0xe80 net/ipv6/addrconf.c:6267
 addrconf_ifdown+0xdfd/0x1950 net/ipv6/addrconf.c:3948
 addrconf_notify+0x39f/0xe30 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455
 call_netdevice_notifiers_info net/core/dev.c:2022 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2060 [inline]
 call_netdevice_notifiers net/core/dev.c:2074 [inline]
 dev_close_many+0x325/0x4d0 net/core/dev.c:1622
 unregister_netdevice_many+0x43f/0x1910 net/core/dev.c:10980
 default_device_exit_batch+0x951/0x9f0 net/core/dev.c:11519
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x630/0xb10 net/core/net_namespace.c:604
 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

The buggy address belongs to the object at ffff8881319cdc00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff8881319cdc00, ffff8881319cde00)

The buggy address belongs to the physical page:
page:ffffea0004c67300 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1319cc
head:ffffea0004c67300 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000001 ffff888100042f00
raw: 0000000000000000 0000000000100010 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 91, tgid 91 (klogd), ts 25622448856, free_ts 0
 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]
 alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6189
 sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2770
 unix_dgram_sendmsg+0x5c1/0x1710 net/unix/af_unix.c:1959
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 __sys_sendto+0x4ac/0x660 net/socket.c:2143
 __do_sys_sendto net/socket.c:2155 [inline]
 __se_sys_sendto net/socket.c:2151 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2151
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881319cdc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881319cdd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881319cdd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8881319cde00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881319cde80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	03 40 0f             	add    0xf(%rax),%eax
   3:	b6 f6                	mov    $0xf6,%dh
   5:	48 b8 01 01 01 01 01 	movabs $0x101010101010101,%rax
   c:	01 01 01
   f:	48 0f af c6          	imul   %rsi,%rax
  13:	f3 48 ab             	rep stos %rax,%es:(%rdi)
  16:	89 d1                	mov    %edx,%ecx
  18:	f3 aa                	rep stos %al,%es:(%rdi)
  1a:	4c 89 c8             	mov    %r9,%rax
  1d:	c3                   	ret
  1e:	90                   	nop
  1f:	49 89 f9             	mov    %rdi,%r9
  22:	40 88 f0             	mov    %sil,%al
  25:	48 89 d1             	mov    %rdx,%rcx
  28:	f3 aa                	rep stos %al,%es:(%rdi)
* 2a:	4c 89 c8             	mov    %r9,%rax <-- trapping instruction
  2d:	c3                   	ret
  2e:	90                   	nop
  2f:	49 89 fa             	mov    %rdi,%r10
  32:	40 0f b6 ce          	movzbl %sil,%ecx
  36:	48 b8 01 01 01 01 01 	movabs $0x101010101010101,%rax
  3d:	01 01 01