==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888131b94190 by task syz.3.212/1249

CPU: 1 PID: 1249 Comm: syz.3.212 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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:ip6_dst_lookup_tail+0x1/0x14e0 net/ipv6/ip6_output.c:1110
Code: c5 03 5e fd 49 c7 06 00 00 00 00 4c 89 e7 4c 89 fe 4c 89 f2 48 89 d9 e8 0d 00 00 00 5b 41 5c 41 5e 41 5f 5d c3 0f 1f 40 00 55 <48> 89 e5 41 57 41 56 41 55 41 54 53 48 83 e4 e0 48 81 ec a0 01 00
RSP: 0018:ffffc90012dd75c8 EFLAGS: 00000293
RAX: ffffffff8458f26f RBX: ffff88811deb0000 RCX: ffffc90012dd7780
RDX: ffffc90012dd75d8 RSI: ffff88811deb0000 RDI: ffff88810e455780
RBP: ffffc90012dd7610 R08: ffffc90012dd77cf R09: 1ffff920025baef9
R10: 0000000000000000 R11: ffffffff823bdcc0 R12: 0000000000000000
R13: ffff88811deb0000 R14: ffffc90012dd7780 R15: ffff88810e455780
 rawv6_sendmsg+0xc92/0x16c0 net/ipv6/raw.c:896
 inet_sendmsg+0xb6/0xd0 net/ipv4/af_inet.c:841
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 ____sys_sendmsg+0x5fb/0x9c0 net/socket.c:2508
 ___sys_sendmsg+0x2a2/0x360 net/socket.c:2562
 __sys_sendmmsg+0x2cc/0x4e0 net/socket.c:2648
 __do_sys_sendmmsg net/socket.c:2677 [inline]
 __se_sys_sendmmsg net/socket.c:2674 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2674
 x64_sys_call+0x3f5/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:308
 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: 0033:0x7f163499ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f16333f7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f1634c15fa0 RCX: 00007f163499ce59
RDX: 00000000000004ff RSI: 00002000000092c0 RDI: 0000000000000006
RBP: 00007f1634a32d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1634c16038 R14: 00007f1634c15fa0 R15: 00007ffc0b1c1068
 </TASK>

Allocated by task 1246:
 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:1609
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:771
 __sys_connect_file net/socket.c:2000 [inline]
 __sys_connect+0x3da/0x460 net/socket.c:2017
 __do_sys_connect net/socket.c:2027 [inline]
 __se_sys_connect net/socket.c:2024 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2024
 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 1085:
 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:1582
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1228 [inline]
 l2tp_tunnel_del_work+0x199/0x410 net/l2tp/l2tp_core.c:1266
 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:1389
 __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

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_route_info_create+0xaa8/0x14d0 net/ipv6/route.c:3878
 ip6_route_add+0x27/0x130 net/ipv6/route.c:3892
 addrconf_prefix_route+0x233/0x310 net/ipv6/addrconf.c:2466
 inet6_addr_add+0x527/0x9c0 net/ipv6/addrconf.c:3042
 inet6_rtm_newaddr+0x74a/0xa10 net/ipv6/addrconf.c:4999
 rtnetlink_rcv_msg+0xb28/0xde0 net/core/rtnetlink.c:6153
 netlink_rcv_skb+0x200/0x450 net/netlink/af_netlink.c:2521
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6171
 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:1873
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 __sys_sendto+0x4ac/0x660 net/socket.c:2142
 __do_sys_sendto net/socket.c:2154 [inline]
 __se_sys_sendto net/socket.c:2150 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2150
 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

The buggy address belongs to the object at ffff888131b94000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff888131b94000, ffff888131b94200)

The buggy address belongs to the physical page:
page:ffffea0004c6e500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x131b94
head:ffffea0004c6e500 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 291, tgid 291 (syz-executor), ts 23910354330, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2679
 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4586
 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5930
 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
 kmalloc_trace+0x29/0xb0 mm/slab_common.c:1028
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 ipv6_add_addr+0x411/0xe80 net/ipv6/addrconf.c:1119
 inet6_addr_add+0x45d/0x9c0 net/ipv6/addrconf.c:3039
 inet6_rtm_newaddr+0x74a/0xa10 net/ipv6/addrconf.c:4999
 rtnetlink_rcv_msg+0xb28/0xde0 net/core/rtnetlink.c:6153
 netlink_rcv_skb+0x200/0x450 net/netlink/af_netlink.c:2521
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6171
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888131b94080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888131b94100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888131b94180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888131b94200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888131b94280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	c5 03 5e fd          	vdivsd %xmm5,%xmm15,%xmm15
   4:	49 c7 06 00 00 00 00 	movq   $0x0,(%r14)
   b:	4c 89 e7             	mov    %r12,%rdi
   e:	4c 89 fe             	mov    %r15,%rsi
  11:	4c 89 f2             	mov    %r14,%rdx
  14:	48 89 d9             	mov    %rbx,%rcx
  17:	e8 0d 00 00 00       	call   0x29
  1c:	5b                   	pop    %rbx
  1d:	41 5c                	pop    %r12
  1f:	41 5e                	pop    %r14
  21:	41 5f                	pop    %r15
  23:	5d                   	pop    %rbp
  24:	c3                   	ret
  25:	0f 1f 40 00          	nopl   0x0(%rax)
  29:	55                   	push   %rbp
* 2a:	48 89 e5             	mov    %rsp,%rbp <-- trapping instruction
  2d:	41 57                	push   %r15
  2f:	41 56                	push   %r14
  31:	41 55                	push   %r13
  33:	41 54                	push   %r12
  35:	53                   	push   %rbx
  36:	48 83 e4 e0          	and    $0xffffffffffffffe0,%rsp
  3a:	48                   	rex.W
  3b:	81                   	.byte 0x81
  3c:	ec                   	in     (%dx),%al
  3d:	a0                   	.byte 0xa0
  3e:	01 00                	add    %eax,(%rax)