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BUG: KASAN: use-after-free in ipv6_gso_pull_exthdrs+0x57a/0x5f0 net/ipv6/ip6_offload.c:45
Read of size 1 at addr ffff8801c8ef0001 by task syz-executor7/23456

CPU: 0 PID: 23456 Comm: syz-executor7 Not tainted 4.18.0-rc3-next-20180706+ #1
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+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
 ipv6_gso_pull_exthdrs+0x57a/0x5f0 net/ipv6/ip6_offload.c:45
 ipv6_gso_segment+0x37a/0x11e0 net/ipv6/ip6_offload.c:87
 skb_mac_gso_segment+0x3b5/0x740 net/core/dev.c:2874
 nsh_gso_segment+0x470/0xb40 net/nsh/nsh.c:111
 skb_mac_gso_segment+0x3b5/0x740 net/core/dev.c:2874
 __skb_gso_segment+0x3c3/0x880 net/core/dev.c:2947
 skb_gso_segment include/linux/netdevice.h:4202 [inline]
 validate_xmit_skb+0x640/0xf30 net/core/dev.c:3186
 __dev_queue_xmit+0xc1f/0x38c0 net/core/dev.c:3674
 dev_queue_xmit+0x17/0x20 net/core/dev.c:3715
 packet_snd net/packet/af_packet.c:2925 [inline]
 packet_sendmsg+0x43e6/0x62e0 net/packet/af_packet.c:2950
 sock_sendmsg_nosec net/socket.c:642 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:652
 __sys_sendto+0x3d7/0x670 net/socket.c:1798
 __do_sys_sendto net/socket.c:1810 [inline]
 __se_sys_sendto net/socket.c:1806 [inline]
 __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1806
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455ba9
Code: 1d ba 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 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007f12cbeb5c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f12cbeb66d4 RCX: 0000000000455ba9
RDX: 0000000000000012 RSI: 0000000020000000 RDI: 0000000000000014
RBP: 000000000072bf48 R08: 00000000200000c0 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004c11b0 R14: 00000000004d1358 R15: 0000000000000001

The buggy address belongs to the page:
page:ffffea000723bc00 count:0 mapcount:-128 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 ffffea0006c8c008 ffffea0006611808 0000000000000000
raw: 0000000000000000 0000000000000003 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c8eeff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c8eeff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8801c8ef0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8801c8ef0080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801c8ef0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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