==================================================================
BUG: KASAN: use-after-free in rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffff888127c65190 by task klogd/90

CPU: 0 PID: 90 Comm: klogd Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <IRQ>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x10f/0x150 mm/kasan/report.c:444
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
 rcu_cblist_dequeue+0x6c/0xb0 kernel/rcu/rcu_segcblist.c:75
 rcu_do_batch+0x412/0xbf0 kernel/rcu/tree.c:2510
 rcu_core+0x4a3/0xef0 kernel/rcu/tree.c:2763
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
 handle_softirqs+0x250/0x560 kernel/softirq.c:583
 __do_softirq kernel/softirq.c:621 [inline]
 invoke_softirq kernel/softirq.c:443 [inline]
 __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:670
 irq_exit_rcu+0x9/0x10 kernel/softirq.c:682
 instr_sysvec_call_function_single arch/x86/kernel/smp.c:243 [inline]
 sysvec_call_function_single+0xa6/0xc0 arch/x86/kernel/smp.c:243
 </IRQ>
 <TASK>
 asm_sysvec_call_function_single+0x1b/0x20 arch/x86/include/asm/idtentry.h:684
RIP: 0010:__sanitizer_cov_trace_pc+0x1/0x60 kernel/kcov.c:199
Code: 00 00 0f 0b 0f 1f 44 00 00 55 48 89 e5 53 48 89 fb e8 13 00 00 00 48 8b 3d 5c 9c 7f 05 48 89 de e8 54 b8 3e 00 5b 5d c3 00 55 <48> 89 e5 48 8b 45 08 65 48 8b 0d c0 c1 98 7e 65 8b 15 c1 c1 98 7e
RSP: 0018:ffffc90000a077f8 EFLAGS: 00000282
RAX: ffffffffffffffec RBX: ffff88810c914d50 RCX: ffff88810d72bb40
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000020
RBP: ffffc90000a078a0 R08: ffffc90000a07717 R09: ffffc90000a076d0
R10: dffffc0000000000 R11: fffff52000140ee3 R12: dffffc0000000000
R13: 1ffff110219229aa R14: 0000000000000000 R15: ffffc90000a07ac0
 avc_compute_av+0x9b/0x820 security/selinux/avc.c:1007
 avc_has_perm_noaudit+0x2cb/0x490 security/selinux/avc.c:1152
 avc_has_perm+0xdd/0x250 security/selinux/avc.c:1187
 sock_has_perm security/selinux/hooks.c:4701 [inline]
 selinux_socket_sendmsg+0x22f/0x340 security/selinux/hooks.c:5055
 security_socket_sendmsg+0x72/0xa0 security/security.c:2254
 __sock_sendmsg net/socket.c:713 [inline]
 __sys_sendto+0x407/0x620 net/socket.c:2062
 __do_sys_sendto net/socket.c:2074 [inline]
 __se_sys_sendto net/socket.c:2070 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2070
 x64_sys_call+0x178/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa882cd5407
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:00007ffe8f0db280 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007fa882b85c80 RCX: 00007fa882cd5407
RDX: 0000000000000082 RSI: 00007ffe8f0db3c0 RDI: 0000000000000003
RBP: 00007ffe8f0db7f0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000004000 R11: 0000000000000202 R12: 00007ffe8f0db808
R13: 00007ffe8f0db3c0 R14: 0000000000000067 R15: 00007ffe8f0db3c0
 </TASK>

Allocated by task 22776:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 ____kasan_kmalloc mm/kasan/common.c:512 [inline]
 __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:521
 kasan_kmalloc include/linux/kasan.h:227 [inline]
 __kmalloc+0x13d/0x2c0 mm/slub.c:4436
 kmalloc include/linux/slab.h:624 [inline]
 kzalloc include/linux/slab.h:750 [inline]
 l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772
 __sys_connect_file net/socket.c:1922 [inline]
 __sys_connect+0x3cb/0x450 net/socket.c:1939
 __do_sys_connect net/socket.c:1949 [inline]
 __se_sys_connect net/socket.c:1946 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1946
 x64_sys_call+0x7c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:43
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 15541:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kfree+0xc4/0x270 mm/slub.c:4588
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_put+0xaf/0x1a0 net/l2tp/l2tp_core.c:193
 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline]
 l2tp_tunnel_del_work+0x180/0x3d0 net/l2tp/l2tp_core.c:1273
 process_one_work+0x6c8/0xbb0 kernel/workqueue.c:2328
 worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475
 kthread+0x3f5/0x4f0 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu_common kernel/rcu/tree.c:3011 [inline]
 call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129
 pppol2tp_release+0x1e3/0x2b0 net/l2tp/l2tp_ppp.c:447
 __sock_release net/socket.c:649 [inline]
 sock_close+0xb8/0x200 net/socket.c:1335
 __fput+0x22b/0x900 fs/file_table.c:311
 ____fput+0x15/0x20 fs/file_table.c:339
 task_work_run+0x127/0x190 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu_common kernel/rcu/tree.c:3011 [inline]
 call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129
 pwq_unbound_release_workfn+0x283/0x2c0 kernel/workqueue.c:-1
 process_one_work+0x6c8/0xbb0 kernel/workqueue.c:2328
 worker_thread+0xaa0/0x1250 kernel/workqueue.c:2475
 kthread+0x3f5/0x4f0 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff888127c65000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff888127c65000, ffff888127c65200)
The buggy address belongs to the page:
page:ffffea00049f1900 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x127c64
head:ffffea00049f1900 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea000477e400 0000000400000004 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 288, ts 24444554320, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa0/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x3ac/0x840 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 __kmalloc_track_caller+0x169/0x2c0 mm/slub.c:4954
 kmalloc_reserve net/core/skbuff.c:357 [inline]
 __alloc_skb+0x210/0x730 net/core/skbuff.c:428
 alloc_skb include/linux/skbuff.h:1183 [inline]
 nlmsg_new include/net/netlink.h:953 [inline]
 inet6_netconf_notify_devconf+0xd6/0x190 net/ipv6/addrconf.c:585
 __addrconf_sysctl_register+0x36e/0x3e0 net/ipv6/addrconf.c:7174
 addrconf_sysctl_register+0x147/0x1a0 net/ipv6/addrconf.c:7211
 ipv6_add_dev+0xc09/0x1150 net/ipv6/addrconf.c:456
 addrconf_notify+0x582/0xe00 net/ipv6/addrconf.c:3600
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:391
 call_netdevice_notifiers_info net/core/dev.c:2070 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2082 [inline]
 call_netdevice_notifiers+0x119/0x190 net/core/dev.c:2096
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888127c65080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888127c65100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888127c65180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888127c65200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888127c65280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================