general protection fault in __ip_append_data

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    f5d582777bcb Merge branch 'for-linus' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16e03afb400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c8970c89a0efbb23
dashboard link: https://syzkaller.appspot.com/bug?extid=aab62b9c7b12e7c6ab0b
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13bb9c8b400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1261667d400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+aab62b9c7b12e7c6ab0b@xxxxxxxxxxxxxxxxxxxxxxxxx

Enabling of bearer <udp:syz1> rejected, already enabled
Enabling of bearer <udp:syz1> rejected, already enabled
Enabling of bearer <udp:syz1> rejected, already enabled
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: 16 Comm: ksoftirqd/1 Not tainted 4.20.0-rc6+ #371
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__ip_append_data.isra.48+0x31a/0x29b0 net/ipv4/ip_output.c:896
Code: c7 85 c8 fd ff ff 00 00 00 00 0f 85 12 10 00 00 e8 7b c1 e0 fa 48 8b  
95 48 fe ff ff 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f  
85 e5 22 00 00 48 8b 85 48 fe ff ff 48 8b 18 48 b8
RSP: 0018:ffff8881d9b569c0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff869ec275
RDX: 0000000000000000 RSI: ffffffff869ec2f5 RDI: 0000000000000001
RBP: ffff8881d9b56c28 R08: ffff8881d9b4a440 R09: ffffffff86b113b0
R10: ffff8881d9b56da0 R11: 0000000000000000 R12: ffff8881d2c18a88
R13: ffffffff86258ba0 R14: ffffffff8bc37110 R15: ffff8881d2c18cd8
FS:  0000000000000000(0000) GS:ffff8881daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001ac0 CR3: 00000001cb6ea000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ip_append_data.part.49+0xef/0x170 net/ipv4/ip_output.c:1197
 ip_append_data+0x6d/0x90 net/ipv4/ip_output.c:1186
 icmp_push_reply+0x18e/0x540 net/ipv4/icmp.c:375
 icmp_send+0x1544/0x1bd0 net/ipv4/icmp.c:736
 __udp4_lib_rcv+0x2484/0x32e0 net/ipv4/udp.c:2233
 udp_rcv+0x21/0x30 net/ipv4/udp.c:2392
 ip_local_deliver_finish+0x2e9/0xda0 net/ipv4/ip_input.c:215
 NF_HOOK include/linux/netfilter.h:289 [inline]
 ip_local_deliver+0x1e9/0x750 net/ipv4/ip_input.c:256
 dst_input include/net/dst.h:450 [inline]
 ip_rcv_finish+0x1f9/0x300 net/ipv4/ip_input.c:415
 NF_HOOK include/linux/netfilter.h:289 [inline]
 ip_rcv+0xed/0x600 net/ipv4/ip_input.c:524
 __netif_receive_skb_one_core+0x14d/0x200 net/core/dev.c:4946
 __netif_receive_skb+0x2c/0x1e0 net/core/dev.c:5056
 process_backlog+0x24e/0x7a0 net/core/dev.c:5864
 napi_poll net/core/dev.c:6287 [inline]
 net_rx_action+0x7fa/0x19b0 net/core/dev.c:6353
 __do_softirq+0x308/0xb7e kernel/softirq.c:292
 run_ksoftirqd+0x5e/0x100 kernel/softirq.c:654
 smpboot_thread_fn+0x68b/0xa00 kernel/smpboot.c:164
 kthread+0x35a/0x440 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace 762165cda5fdc138 ]---
Enabling of bearer <udp:syz1> rejected, already enabled
RIP: 0010:__ip_append_data.isra.48+0x31a/0x29b0 net/ipv4/ip_output.c:896
Code: c7 85 c8 fd ff ff 00 00 00 00 0f 85 12 10 00 00 e8 7b c1 e0 fa 48 8b  
95 48 fe ff ff 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f  
85 e5 22 00 00 48 8b 85 48 fe ff ff 48 8b 18 48 b8
Enabling of bearer <udp:syz1> rejected, already enabled
RSP: 0018:ffff8881d9b569c0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff869ec275
RDX: 0000000000000000 RSI: ffffffff869ec2f5 RDI: 0000000000000001
RBP: ffff8881d9b56c28 R08: ffff8881d9b4a440 R09: ffffffff86b113b0
R10: ffff8881d9b56da0 R11: 0000000000000000 R12: ffff8881d2c18a88
R13: ffffffff86258ba0 R14: ffffffff8bc37110 R15: ffff8881d2c18cd8
Enabling of bearer <udp:syz1> rejected, already enabled
FS:  0000000000000000(0000) GS:ffff8881daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001ac0 CR3: 000000000946a000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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