general protection fault in ip6erspan_set_version

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    cb916fc5eabf Add linux-next specific files for 20190218
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15111104c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6ef0fb4978ed6ac0
dashboard link: https://syzkaller.appspot.com/bug?extid=30191cf1057abd3064af
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1198a582c00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=142f37bcc00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+30191cf1057abd3064af@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 7549 Comm: syz-executor432 Not tainted 5.0.0-rc6-next-20190218  
#37
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:ip6erspan_set_version+0x5c/0x350 net/ipv6/ip6_gre.c:1726
Code: 07 38 d0 7f 08 84 c0 0f 85 9f 02 00 00 49 8d bc 24 b0 00 00 00 c6 43  
54 01 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 9a 02 00 00 4d 8b ac 24 b0 00 00 00 4d 85 ed 0f
RSP: 0018:ffff888089ed7168 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8880869d6e58 RCX: 0000000000000000
RDX: 0000000000000016 RSI: ffffffff862736b4 RDI: 00000000000000b0
RBP: ffff888089ed7180 R08: 1ffff11010d3adcb R09: ffff8880869d6e58
R10: ffffed1010d3add5 R11: ffff8880869d6eaf R12: 0000000000000000
R13: ffffffff8931f8c0 R14: ffffffff862825d0 R15: ffff8880869d6e58
FS:  0000000000b3d880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000184 CR3: 0000000092cc5000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ip6erspan_newlink+0x66/0x7b0 net/ipv6/ip6_gre.c:2210
 __rtnl_newlink+0x107b/0x16c0 net/core/rtnetlink.c:3176
 rtnl_newlink+0x69/0xa0 net/core/rtnetlink.c:3234
 rtnetlink_rcv_msg+0x465/0xb00 net/core/rtnetlink.c:5192
 netlink_rcv_skb+0x17a/0x460 net/netlink/af_netlink.c:2485
 rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5210
 netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
 netlink_unicast+0x536/0x720 net/netlink/af_netlink.c:1336
 netlink_sendmsg+0x8ae/0xd70 net/netlink/af_netlink.c:1925
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg+0xdd/0x130 net/socket.c:631
 ___sys_sendmsg+0x806/0x930 net/socket.c:2136
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2174
 __do_sys_sendmsg net/socket.c:2183 [inline]
 __se_sys_sendmsg net/socket.c:2181 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2181
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440159
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffa69156e8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440159
RDX: 0000000000000000 RSI: 0000000020001340 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000001 R09: 00000000004002c8
R10: 0000000000000011 R11: 0000000000000246 R12: 00000000004019e0
R13: 0000000000401a70 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 09f8a7d13b4faaa1 ]---
RIP: 0010:ip6erspan_set_version+0x5c/0x350 net/ipv6/ip6_gre.c:1726
Code: 07 38 d0 7f 08 84 c0 0f 85 9f 02 00 00 49 8d bc 24 b0 00 00 00 c6 43  
54 01 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 9a 02 00 00 4d 8b ac 24 b0 00 00 00 4d 85 ed 0f
RSP: 0018:ffff888089ed7168 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8880869d6e58 RCX: 0000000000000000
RDX: 0000000000000016 RSI: ffffffff862736b4 RDI: 00000000000000b0
RBP: ffff888089ed7180 R08: 1ffff11010d3adcb R09: ffff8880869d6e58
R10: ffffed1010d3add5 R11: ffff8880869d6eaf R12: 0000000000000000
R13: ffffffff8931f8c0 R14: ffffffff862825d0 R15: ffff8880869d6e58
FS:  0000000000b3d880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000184 CR3: 0000000092cc5000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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