general protection fault in tipc_sk_fill_sock_diag

[syzbot]

Hello,

syzbot hit the following crash on net-next commit
94cb5492409219ee3f9468616dd58af314029f76 (Fri Mar 23 18:31:30 2018 +0000)
net/sched: act_vlan: declare push_vid with host byte order
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=326e587eff1074657718

So far this crash happened 8 times on net-next.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5316828523921408
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=5398288350052352
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=5097949340106752
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=2445237949826843652
compiler: gcc (GCC) 7.1.1 20170620

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Reported-by: syzbot+326e587eff1074657718@xxxxxxxxxxxxxxxxxxxxxxxxx
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

audit: type=1400 audit(1522009585.022:6): avc:  denied  { map } for   
pid=4261 comm="bash" path="/bin/bash" dev="sda1" ino=1457  
scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
audit: type=1400 audit(1522009597.461:7): avc:  denied  { map } for   
pid=4277 comm="syzkaller549428" path="/root/syzkaller549428900" dev="sda1"  
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4277 Comm: syzkaller549428 Not tainted 4.16.0-rc6+ #280
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:sk_user_ns include/net/sock.h:748 [inline]
RIP: 0010:tipc_sk_fill_sock_diag+0x42d/0xc00 net/tipc/socket.c:3282
RSP: 0018:ffff8801b017eff0 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 1ffff1003602fe04 RCX: 000000000000002b
RDX: dffffc0000000000 RSI: 1ffff10035d4b577 RDI: 0000000000000158
RBP: ffff8801b017f2a8 R08: 1ffff1003602fdbf R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d1637740
R13: ffff8801b0d50d40 R14: ffff8801b017f280 R15: 0000000000000000
FS:  00000000014a6880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020005000 CR3: 00000001b01b3005 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __tipc_add_sock_diag+0x20e/0x330 net/tipc/diag.c:62
 tipc_nl_sk_walk+0x565/0xb60 net/tipc/socket.c:3240
 tipc_diag_dump+0x24/0x30 net/tipc/diag.c:73
 netlink_dump+0x492/0xcf0 net/netlink/af_netlink.c:2222
 __netlink_dump_start+0x4ec/0x710 net/netlink/af_netlink.c:2319
 netlink_dump_start include/linux/netlink.h:214 [inline]
 tipc_sock_diag_handler_dump+0x206/0x2c0 net/tipc/diag.c:89
 __sock_diag_cmd net/core/sock_diag.c:230 [inline]
 sock_diag_rcv_msg+0x204/0x360 net/core/sock_diag.c:261
 netlink_rcv_skb+0x14b/0x380 net/netlink/af_netlink.c:2444
 sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:272
 netlink_unicast_kernel net/netlink/af_netlink.c:1308 [inline]
 netlink_unicast+0x4c4/0x6b0 net/netlink/af_netlink.c:1334
 netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1897
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:639
 ___sys_sendmsg+0x767/0x8b0 net/socket.c:2047
 __sys_sendmsg+0xe5/0x210 net/socket.c:2081
 SYSC_sendmsg net/socket.c:2092 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2088
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x43fde9
RSP: 002b:00007ffc6f197198 EFLAGS: 00000213 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fde9
RDX: 0000000000000000 RSI: 0000000020005000 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000213 R12: 0000000000401710
R13: 00000000004017a0 R14: 0000000000000000 R15: 0000000000000000
Code: f9 48 c1 e9 03 80 3c 11 00 0f 85 b5 07 00 00 4d 8b 7f 18 48 ba 00 00  
00 00 00 fc ff df 49 8d bf 58 01 00 00 48 89 f9 48 c1 e9 03 <80> 3c 11 00  
0f 85 2b 07 00 00 4d 8b bf 58 01 00 00 48 ba 00 00
RIP: sk_user_ns include/net/sock.h:748 [inline] RSP: ffff8801b017eff0
RIP: tipc_sk_fill_sock_diag+0x42d/0xc00 net/tipc/socket.c:3282 RSP:  
ffff8801b017eff0
---[ end trace ae417c2a60a8b333 ]---


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