Re: general protection fault in nft_chain_parse_hook

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    f5ae2ea6 Fix built-in early-load Intel microcode alignment
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=112c92d1e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d9290aeb7e6cf1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=156a04714799b1d480bc
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=110253aee00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=170d8159e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+156a04714799b1d480bc@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: 0 PID: 9678 Comm: syz-executor546 Not tainted 5.5.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:nft_chain_parse_hook+0x386/0xa10  
net/netfilter/nf_tables_api.c:1767
Code: e8 5f 27 0e fb 41 83 fd 05 0f 87 62 05 00 00 e8 d0 25 0e fb 49 8d 7c  
24 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84  
c0 74 08 3c 03 0f 8e a6 05 00 00 44 89 e9 be 01 00
RSP: 0018:ffffc900021370f0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffffc900021372a0 RCX: ffffffff8666cfa1
RDX: 0000000000000003 RSI: ffffffff8666cfb0 RDI: 0000000000000018
RBP: ffffc900021371e0 R08: ffff88809c7ce380 R09: 0000000000000000
R10: fffff52000426e2d R11: ffffc9000213716f R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc900021371b8
FS:  0000000000000000(0000) GS:ffff8880ae800000(0063) knlGS:0000000009dfd840
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000020000280 CR3: 00000000a29dd000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 nf_tables_addchain.constprop.0+0x1c1/0x1520  
net/netfilter/nf_tables_api.c:1888
 nf_tables_newchain+0x1033/0x1820 net/netfilter/nf_tables_api.c:2196
 nfnetlink_rcv_batch+0xf42/0x17a0 net/netfilter/nfnetlink.c:433
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:543 [inline]
 nfnetlink_rcv+0x3e7/0x460 net/netfilter/nfnetlink.c:561
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x58c/0x7d0 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:659
 ____sys_sendmsg+0x753/0x880 net/socket.c:2330
 ___sys_sendmsg+0x100/0x170 net/socket.c:2384
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2417
 __compat_sys_sendmsg net/compat.c:642 [inline]
 __do_compat_sys_sendmsg net/compat.c:649 [inline]
 __se_compat_sys_sendmsg net/compat.c:646 [inline]
 __ia32_compat_sys_sendmsg+0x7a/0xb0 net/compat.c:646
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fafa39
Code: 00 00 00 89 d3 5b 5e 5f 5d c3 b8 80 96 98 00 eb c4 8b 04 24 c3 8b 1c  
24 c3 8b 34 24 c3 8b 3c 24 c3 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90  
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000ffc60f6c EFLAGS: 00000202 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000002000d400
RDX: 0000000004000000 RSI: 00000000080ea00c RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace ef2c8b24d08b7122 ]---
RIP: 0010:nft_chain_parse_hook+0x386/0xa10  
net/netfilter/nf_tables_api.c:1767
Code: e8 5f 27 0e fb 41 83 fd 05 0f 87 62 05 00 00 e8 d0 25 0e fb 49 8d 7c  
24 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84  
c0 74 08 3c 03 0f 8e a6 05 00 00 44 89 e9 be 01 00
RSP: 0018:ffffc900021370f0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffffc900021372a0 RCX: ffffffff8666cfa1
RDX: 0000000000000003 RSI: ffffffff8666cfb0 RDI: 0000000000000018
RBP: ffffc900021371e0 R08: ffff88809c7ce380 R09: 0000000000000000
R10: fffff52000426e2d R11: ffffc9000213716f R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc900021371b8
FS:  0000000000000000(0000) GS:ffff8880ae800000(0063) knlGS:0000000009dfd840
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000020000280 CR3: 00000000a29dd000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400