general protection fault in tipc_nl_publ_dump

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    056ddc38 Merge branch 'stmmac-next'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=168bdd47600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d9be300620399522
dashboard link: https://syzkaller.appspot.com/bug?extid=8d37c50ffb0f52941a5e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11ad0d0b600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=113f6d47600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8d37c50ffb0f52941a5e@xxxxxxxxxxxxxxxxxxxxxxxxx

netlink: 20 bytes leftover after parsing attributes in process  
`syz-executor671'.
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: 8721 Comm: syz-executor671 Not tainted 5.4.0-rc1+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:tipc_nl_publ_dump+0x1c3/0xd60 net/tipc/socket.c:3591
Code: 80 3c 02 00 0f 85 9d 09 00 00 48 8b 85 f0 fe ff ff 4c 8b 70 20 48 b8  
00 00 00 00 00 fc ff df 49 8d 7e 10 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 69 09 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b
RSP: 0018:ffff88808e2c6eb8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff870875af
RDX: 0000000000000002 RSI: ffffffff870875bd RDI: 0000000000000010
RBP: ffff88808e2c7040 R08: ffff888093c7a300 R09: ffffed1015d06b75
R10: ffffed1015d06b74 R11: ffff8880ae835ba3 R12: ffffffff89986140
R13: 0000000000000000 R14: 0000000000000000 R15: ffff8880a97b28c0
FS:  0000000002434880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043e990 CR3: 0000000093db1000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __tipc_nl_compat_dumpit.isra.0+0x274/0xa80 net/tipc/netlink_compat.c:215
 tipc_nl_compat_publ_dump net/tipc/netlink_compat.c:1013 [inline]
 tipc_nl_compat_sk_dump+0x54d/0x970 net/tipc/netlink_compat.c:1065
 __tipc_nl_compat_dumpit.isra.0+0x3fb/0xa80 net/tipc/netlink_compat.c:226
 tipc_nl_compat_dumpit+0x24c/0x510 net/tipc/netlink_compat.c:299
 tipc_nl_compat_handle net/tipc/netlink_compat.c:1264 [inline]
 tipc_nl_compat_recv+0x5a0/0xae0 net/tipc/netlink_compat.c:1302
 genl_family_rcv_msg_doit net/netlink/genetlink.c:668 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:713 [inline]
 genl_rcv_msg+0x678/0x1000 net/netlink/genetlink.c:730
 netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
 genl_rcv+0x29/0x40 net/netlink/genetlink.c:741
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x531/0x710 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x8a5/0xd60 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:657
 ___sys_sendmsg+0x803/0x920 net/socket.c:2311
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2356
 __do_sys_sendmsg net/socket.c:2365 [inline]
 __se_sys_sendmsg net/socket.c:2363 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2363
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4441b9
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 1b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd2b43b478 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 00000000004441b9
RDX: 0000000000000000 RSI: 0000000020000500 RDI: 0000000000000003
RBP: 00000000006ce018 R08: 0000000000000000 R09: 00000000004002e0
R10: 0000000000001900 R11: 0000000000000246 R12: 0000000000401e60
R13: 0000000000401ef0 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 854b542c9f3952ec ]---
RIP: 0010:tipc_nl_publ_dump+0x1c3/0xd60 net/tipc/socket.c:3591
Code: 80 3c 02 00 0f 85 9d 09 00 00 48 8b 85 f0 fe ff ff 4c 8b 70 20 48 b8  
00 00 00 00 00 fc ff df 49 8d 7e 10 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 69 09 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b
RSP: 0018:ffff88808e2c6eb8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff870875af
RDX: 0000000000000002 RSI: ffffffff870875bd RDI: 0000000000000010
RBP: ffff88808e2c7040 R08: ffff888093c7a300 R09: ffffed1015d06b75
R10: ffffed1015d06b74 R11: ffff8880ae835ba3 R12: ffffffff89986140
R13: 0000000000000000 R14: 0000000000000000 R15: ffff8880a97b28c0
FS:  0000000002434880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043e990 CR3: 0000000093db1000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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