TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
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BUG: KASAN: null-ptr-deref in atomic_sub_return include/asm-generic/atomic-instrumented.h:305 [inline]
BUG: KASAN: null-ptr-deref in dst_release net/core/dst.c:186 [inline]
BUG: KASAN: null-ptr-deref in dst_release+0x2a/0xb0 net/core/dst.c:181
Write of size 4 at addr 000000000000013c by task syz-executor.0/21644

CPU: 1 PID: 21644 Comm: syz-executor.0 Not tainted 5.0.0-rc8+ #108
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 kasan_report.cold+0x5/0x40 mm/kasan/report.c:321
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 kasan_check_write+0x14/0x20 mm/kasan/common.c:106
 atomic_sub_return include/asm-generic/atomic-instrumented.h:305 [inline]
 dst_release net/core/dst.c:186 [inline]
 dst_release+0x2a/0xb0 net/core/dst.c:181
 dst_cache_destroy net/core/dst_cache.c:164 [inline]
 dst_cache_destroy+0xd3/0x1b0 net/core/dst_cache.c:156
 ip_tunnel_dev_free+0x25/0x60 net/ipv4/ip_tunnel.c:967
 netdev_run_todo+0x51c/0x7d0 net/core/dev.c:8888
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:117
 ip_tunnel_delete_nets+0x423/0x5f0 net/ipv4/ip_tunnel.c:1080
 vti_exit_batch_net+0x23/0x30 net/ipv4/ip_vti.c:495
 ops_exit_list.isra.0+0x105/0x160 net/core/net_namespace.c:156
 setup_net+0x3f2/0x730 net/core/net_namespace.c:331
 copy_net_ns+0x1d9/0x340 net/core/net_namespace.c:437
 create_new_namespaces+0x400/0x7b0 kernel/nsproxy.c:107
 unshare_nsproxy_namespaces+0xc2/0x200 kernel/nsproxy.c:206
 ksys_unshare+0x440/0x980 kernel/fork.c:2550
 __do_sys_unshare kernel/fork.c:2618 [inline]
 __se_sys_unshare kernel/fork.c:2616 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:2616
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457e29
Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4882b09c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000457e29
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4882b0a6d4
R13: 00000000004c6c3b R14: 00000000004dc3f8 R15: 00000000ffffffff
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