net: BUG in __skb_gso_segment

Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

A reproducer and .config are attached.

On commit 926af6273fc683cd98cd0ce7bf0d04a02eed6742.

kernel BUG at ./include/linux/skbuff.h:1942!
invalid opcode: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 5922 Comm: syz-executor5 Not tainted 4.10.0-rc7+ #127
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88003ba72dc0 task.stack: ffff880033ed0000
RIP: 0010:__skb_pull include/linux/skbuff.h:1942 [inline]
RIP: 0010:skb_mac_gso_segment+0x5ae/0x690 net/core/dev.c:2634
RSP: 0018:ffff880033ed6c48 EFLAGS: 00010216
RAX: 0000000000010000 RBX: 000000000000113e RCX: ffffc90003f74000
RDX: 0000000000000223 RSI: ffffffff833cfbfe RDI: ffff88003e305244
RBP: ffff880033ed6d98 R08: 0000000000000000 R09: 0000000000000000
R10: c66e14bf8d4328e9 R11: 0000000000000000 R12: 000000000000000e
R13: ffff88003e3051c0 R14: ffff880033ed6d70 R15: 0000000000000000
FS:  00007faa035db700(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000203dd000 CR3: 000000003c165000 CR4: 00000000000006e0
Call Trace:
 __skb_gso_segment+0x3d2/0x780 net/core/dev.c:2710
 skb_gso_segment include/linux/netdevice.h:3914 [inline]
 validate_xmit_skb+0x5c9/0xc20 net/core/dev.c:2944
 __dev_queue_xmit+0x102e/0x2860 net/core/dev.c:3364
 dev_queue_xmit+0x17/0x20 net/core/dev.c:3405
 packet_snd net/packet/af_packet.c:2872 [inline]
 packet_sendmsg+0x40bc/0x58b0 net/packet/af_packet.c:2897
 sock_sendmsg_nosec net/socket.c:635 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:645
 ___sys_sendmsg+0x4a3/0xae0 net/socket.c:1985
 __sys_sendmmsg+0x25c/0x750 net/socket.c:2075
 SYSC_sendmmsg net/socket.c:2106 [inline]
 SyS_sendmmsg+0x35/0x60 net/socket.c:2101
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x4458b9
RSP: 002b:00007faa035dab58 EFLAGS: 00000292 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 0000000000000016 RCX: 00000000004458b9
RDX: 0000000000000001 RSI: 0000000020bc7fc8 RDI: 0000000000000016
RBP: 00000000006e1ad0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000708000
R13: 0000000020fcc000 R14: 0000000000001000 R15: 0000000000000003
Code: 00 00 48 c7 c7 00 4b 23 85 c6 05 b6 6f b2 02 01 e8 58 7a 04 fe
e9 ae fc ff ff 48 c7 c3 ea ff ff ff e9 dc fe ff ff e8 82 f0 1d fe <0f>
0b 48 8b bd e0 fe ff ff e8 a4 30 48 fe e9 ef fd ff ff e8 9a
RIP: __skb_pull include/linux/skbuff.h:1942 [inline] RSP: ffff880033ed6c48
RIP: skb_mac_gso_segment+0x5ae/0x690 net/core/dev.c:2634 RSP: ffff880033ed6c48
---[ end trace 2214c8475331c97c ]---
Kernel panic - not syncing: Fatal exception in interrupt
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..