TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
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BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline]
BUG: KASAN: use-after-free in atomic_read arch/x86/include/asm/atomic.h:27 [inline]
BUG: KASAN: use-after-free in refcount_inc_not_zero+0xd3/0xe0 lib/refcount.c:120
Read of size 4 at addr ffff88809c3895c0 by task kworker/u4:2/157

CPU: 1 PID: 157 Comm: kworker/u4:2 Not tainted 4.14.141 #37
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x138/0x197 lib/dump_stack.c:53
 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
 __read_once_size include/linux/compiler.h:183 [inline]
 atomic_read arch/x86/include/asm/atomic.h:27 [inline]
 refcount_inc_not_zero+0xd3/0xe0 lib/refcount.c:120
 refcount_inc+0x16/0x40 lib/refcount.c:153
 sock_hold include/net/sock.h:619 [inline]
 pppol2tp_session_sock_hold+0x48/0x60 net/l2tp/l2tp_ppp.c:263
 l2tp_tunnel_closeall+0x1ef/0x380 net/l2tp/l2tp_core.c:1332
 l2tp_tunnel_del_work+0x64/0x410 net/l2tp/l2tp_core.c:1380
 process_one_work+0x863/0x1600 kernel/workqueue.c:2114
 worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
 kthread+0x319/0x430 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 2244:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
 __do_kmalloc_node mm/slab.c:3682 [inline]
 __kmalloc_node_track_caller+0x51/0x80 mm/slab.c:3696
 __kmalloc_reserve.isra.0+0x40/0xe0 net/core/skbuff.c:137
 __alloc_skb+0xcf/0x500 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:980 [inline]
 nlmsg_new include/net/netlink.h:511 [inline]
 rtmsg_ifinfo_build_skb+0x72/0x140 net/core/rtnetlink.c:2878
 rollback_registered_many+0x78f/0xb60 net/core/dev.c:7217
 unregister_netdevice_many.part.0+0x1b/0x1e0 net/core/dev.c:8265
 unregister_netdevice_many+0x3b/0x50 net/core/dev.c:8264
 vti6_destroy_tunnels net/ipv6/ip6_vti.c:1077 [inline]
 vti6_exit_net+0x332/0x4a0 net/ipv6/ip6_vti.c:1122
 ops_exit_list.isra.0+0xaa/0x150 net/core/net_namespace.c:142
 cleanup_net+0x3ba/0x880 net/core/net_namespace.c:484
 process_one_work+0x863/0x1600 kernel/workqueue.c:2114
 worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
 kthread+0x319/0x430 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Freed by task 2244:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcc/0x270 mm/slab.c:3815
 skb_free_head+0x8b/0xb0 net/core/skbuff.c:554
 skb_release_data+0x4af/0x700 net/core/skbuff.c:574
 skb_release_all+0x4d/0x60 net/core/skbuff.c:631
 __kfree_skb net/core/skbuff.c:645 [inline]
 consume_skb+0xaf/0x340 net/core/skbuff.c:705
 netlink_broadcast_filtered+0x2ae/0x9f0 net/netlink/af_netlink.c:1488
 netlink_broadcast net/netlink/af_netlink.c:1510 [inline]
 nlmsg_multicast include/net/netlink.h:591 [inline]
 nlmsg_notify+0x7c/0x190 net/netlink/af_netlink.c:2475
 rtnl_notify net/core/rtnetlink.c:653 [inline]
 rtmsg_ifinfo_send+0x76/0x8b net/core/rtnetlink.c:2900
 rollback_registered_many+0x81e/0xb60 net/core/dev.c:7230
 unregister_netdevice_many.part.0+0x1b/0x1e0 net/core/dev.c:8265
 unregister_netdevice_many+0x3b/0x50 net/core/dev.c:8264
 vti6_destroy_tunnels net/ipv6/ip6_vti.c:1077 [inline]
 vti6_exit_net+0x332/0x4a0 net/ipv6/ip6_vti.c:1122
 ops_exit_list.isra.0+0xaa/0x150 net/core/net_namespace.c:142
 cleanup_net+0x3ba/0x880 net/core/net_namespace.c:484
 process_one_work+0x863/0x1600 kernel/workqueue.c:2114
 worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
 kthread+0x319/0x430 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

The buggy address belongs to the object at ffff88809c389540
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 128 bytes inside of
 2048-byte region [ffff88809c389540, ffff88809c389d40)
The buggy address belongs to the page:
page:ffffea000270e200 count:1 mapcount:0 mapping:ffff88809c388440 index:0xffff88809c388cc0 compound_mapcount: 0
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffff88809c388440 ffff88809c388cc0 0000000100000002
raw: ffffea00018414a0 ffffea00017dc2a0 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809c389480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88809c389500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff88809c389580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff88809c389600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809c389680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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