Re: kernel BUG at net/ipv4/ip_output.c:LINE!

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    112cbae26d18 Merge branch 'linus' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1192ae72400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=152cb8ccd35b1f70
dashboard link: https://syzkaller.appspot.com/bug?extid=90d5ec0c05e708f3b66d
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=153ed6e2400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1539038c400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+90d5ec0c05e708f3b66d@xxxxxxxxxxxxxxxxxxxxxxxxx

IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0
------------[ cut here ]------------
kernel BUG at net/ipv4/ip_output.c:775!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 1 PID: 4713 Comm: syz-executor450 Not tainted 4.18.0-rc8+ #182
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:ip_do_fragment+0x2436/0x2aa0 net/ipv4/ip_output.c:775
Code: 8b 8d 70 fe ff ff e9 99 e8 ff ff 4c 89 ef e8 a1 65 40 fc e9 7b e9 ff  
ff 4c 89 f7 e8 94 65 40 fc e9 f3 e5 ff ff e8 7a 89 02 fc <0f> 0b 4c 89 e7  
e8 80 65 40 fc e9 b7 e8 ff ff 4c 89 f7 89 8d 70 fe
RSP: 0018:ffff8801cfe3e880 EFLAGS: 00010293
RAX: ffff8801af542080 RBX: ffff8801c88eaa00 RCX: ffffffff85797886
RDX: 0000000000000000 RSI: ffffffff85798ed6 RDI: 0000000000000005
RBP: ffff8801cfe3ea58 R08: ffff8801af542080 R09: ffffed0039110032
R10: ffffed0039110034 R11: ffff8801c88801a3 R12: ffff8801c88eaac4
R13: 00000000fffffff2 R14: ffff8801c88eaad0 R15: dffffc0000000000
FS:  0000000001479880(0000) GS:ffff8801db100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 00000001cf669000 CR4: 00000000001406e0
Call Trace:
 ip_fragment.constprop.49+0x179/0x240 net/ipv4/ip_output.c:548
 ip_finish_output+0x6e4/0xfa0 net/ipv4/ip_output.c:315
 NF_HOOK_COND include/linux/netfilter.h:276 [inline]
 ip_output+0x223/0x880 net/ipv4/ip_output.c:405
 dst_output include/net/dst.h:444 [inline]
 ip_local_out+0xc5/0x1b0 net/ipv4/ip_output.c:124
 iptunnel_xmit+0x53b/0x800 net/ipv4/ip_tunnel_core.c:91
 ip_tunnel_xmit+0x1598/0x3af1 net/ipv4/ip_tunnel.c:778
 __gre_xmit+0x5b7/0x950 net/ipv4/ip_gre.c:449
 ipgre_xmit+0x3e8/0xb50 net/ipv4/ip_gre.c:701
 __netdev_start_xmit include/linux/netdevice.h:4148 [inline]
 netdev_start_xmit include/linux/netdevice.h:4157 [inline]
 xmit_one net/core/dev.c:3034 [inline]
 dev_hard_start_xmit+0x26c/0xc30 net/core/dev.c:3050
 __dev_queue_xmit+0x29c2/0x38e0 net/core/dev.c:3569
 dev_queue_xmit+0x17/0x20 net/core/dev.c:3602
 __bpf_tx_skb net/core/filter.c:1995 [inline]
 __bpf_redirect_common net/core/filter.c:2033 [inline]
 __bpf_redirect+0x563/0xa80 net/core/filter.c:2040
 ____bpf_clone_redirect net/core/filter.c:2073 [inline]
 bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2045
 bpf_prog_bebbfe2050753572+0xef4/0x1000
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace b3cbe48b5e178b8d ]---
RIP: 0010:ip_do_fragment+0x2436/0x2aa0 net/ipv4/ip_output.c:775
Code: 8b 8d 70 fe ff ff e9 99 e8 ff ff 4c 89 ef e8 a1 65 40 fc e9 7b e9 ff  
ff 4c 89 f7 e8 94 65 40 fc e9 f3 e5 ff ff e8 7a 89 02 fc <0f> 0b 4c 89 e7  
e8 80 65 40 fc e9 b7 e8 ff ff 4c 89 f7 89 8d 70 fe
RSP: 0018:ffff8801cfe3e880 EFLAGS: 00010293
RAX: ffff8801af542080 RBX: ffff8801c88eaa00 RCX: ffffffff85797886
RDX: 0000000000000000 RSI: ffffffff85798ed6 RDI: 0000000000000005
RBP: ffff8801cfe3ea58 R08: ffff8801af542080 R09: ffffed0039110032
R10: ffffed0039110034 R11: ffff8801c88801a3 R12: ffff8801c88eaac4
R13: 00000000fffffff2 R14: ffff8801c88eaad0 R15: dffffc0000000000
FS:  0000000001479880(0000) GS:ffff8801db100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 00000001cf669000 CR4: 00000000001406e0