general protection fault in nf_ct_netns_do_get

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    46cf053e Linux 5.5-rc3
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14188971e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ed9d672709340e35
dashboard link: https://syzkaller.appspot.com/bug?extid=19616eedf6fd8e241e50
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14a47ab9e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=170f2485e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+19616eedf6fd8e241e50@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: 9171 Comm: syz-executor797 Not tainted 5.5.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:199 [inline]
RIP: 0010:net_generic include/net/netns/generic.h:45 [inline]
RIP: 0010:nf_ct_netns_do_get+0xd2/0x7e0  
net/netfilter/nf_conntrack_proto.c:449
Code: 22 22 fb 45 84 f6 0f 84 5c 03 00 00 e8 07 21 22 fb 49 8d bc 24 68 13  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 9f 06 00 00 4d 8b b4 24 68 13 00 00 e8 47 59 0e
RSP: 0018:ffffc90001f177a8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000003 RCX: ffffffff86531056
RDX: 000000000000026d RSI: ffffffff86530ce9 RDI: 0000000000001368
RBP: ffffc90001f177e8 R08: ffff88808fd96200 R09: ffffed1015d0703d
R10: ffffed1015d0703c R11: ffff8880ae8381e3 R12: 0000000000000000
R13: 000000000000002a R14: 0000000000000001 R15: 0000000000000003
FS:  00000000009fd880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200008a0 CR3: 0000000093cc3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 nf_ct_netns_get+0x41/0x150 net/netfilter/nf_conntrack_proto.c:601
 connmark_tg_check+0x61/0xe0 net/netfilter/xt_connmark.c:106
 xt_check_target+0x283/0x690 net/netfilter/x_tables.c:1019
 check_target net/ipv4/netfilter/arp_tables.c:399 [inline]
 find_check_entry net/ipv4/netfilter/arp_tables.c:422 [inline]
 translate_table+0x1005/0x1d70 net/ipv4/netfilter/arp_tables.c:572
 do_replace net/ipv4/netfilter/arp_tables.c:977 [inline]
 do_arpt_set_ctl+0x310/0x640 net/ipv4/netfilter/arp_tables.c:1456
 nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
 nf_setsockopt+0x77/0xd0 net/netfilter/nf_sockopt.c:115
 ip_setsockopt net/ipv4/ip_sockglue.c:1260 [inline]
 ip_setsockopt+0xdf/0x100 net/ipv4/ip_sockglue.c:1240
 udp_setsockopt+0x68/0xb0 net/ipv4/udp.c:2639
 sock_common_setsockopt+0x94/0xd0 net/core/sock.c:3149
 __sys_setsockopt+0x261/0x4c0 net/socket.c:2117
 __do_sys_setsockopt net/socket.c:2133 [inline]
 __se_sys_setsockopt net/socket.c:2130 [inline]
 __x64_sys_setsockopt+0xbe/0x150 net/socket.c:2130
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441369
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:00007ffed53f1838 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000441369
RDX: 0000000000000060 RSI: 0a02000000000000 RDI: 0000000000000003
RBP: 00000000006cb018 R08: 0000000000000418 R09: 00000000004002c8
R10: 0000000020000880 R11: 0000000000000246 R12: 0000000000402bf0
R13: 0000000000402c80 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 86b70d3f20194272 ]---
RIP: 0010:__read_once_size include/linux/compiler.h:199 [inline]
RIP: 0010:net_generic include/net/netns/generic.h:45 [inline]
RIP: 0010:nf_ct_netns_do_get+0xd2/0x7e0  
net/netfilter/nf_conntrack_proto.c:449
Code: 22 22 fb 45 84 f6 0f 84 5c 03 00 00 e8 07 21 22 fb 49 8d bc 24 68 13  
00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 9f 06 00 00 4d 8b b4 24 68 13 00 00 e8 47 59 0e
RSP: 0018:ffffc90001f177a8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000003 RCX: ffffffff86531056
RDX: 000000000000026d RSI: ffffffff86530ce9 RDI: 0000000000001368
RBP: ffffc90001f177e8 R08: ffff88808fd96200 R09: ffffed1015d0703d
R10: ffffed1015d0703c R11: ffff8880ae8381e3 R12: 0000000000000000
R13: 000000000000002a R14: 0000000000000001 R15: 0000000000000003
FS:  00000000009fd880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200008a0 CR3: 0000000093cc3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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