Re: KMSAN: uninit-value in __inet6_bind

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    0a602458c72c kmsan: random: another take at unpoisoning CR..
git tree:       https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=129e1035400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9b071100dcf8e641
dashboard link: https://syzkaller.appspot.com/bug?extid=c56449ed3652e6720f30
compiler:       clang version 8.0.0 (trunk 348261)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10a97b2b400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=108ec72b400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c56449ed3652e6720f30@xxxxxxxxxxxxxxxxxxxxxxxxx

audit: type=1800 audit(1545030606.944:30): pid=6407 uid=0 auid=4294967295  
ses=4294967295 subj==unconfined op=collect_data cause=failed(directio)  
comm="startpar" name="rmnologin" dev="sda1" ino=2423 res=0
Started in network mode
Own node identity fe8000000000000000000000000000bb, cluster identity 4711
==================================================================
BUG: KMSAN: uninit-value in __inet6_bind+0xb35/0x1a30  
net/ipv6/af_inet6.c:340
CPU: 1 PID: 6557 Comm: syz-executor447 Not tainted 4.20.0-rc5+ #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x220 lib/dump_stack.c:113
 kmsan_report+0x12d/0x290 mm/kmsan/kmsan.c:682
 __msan_warning+0x76/0xc0 mm/kmsan/kmsan_instr.c:316
 __inet6_bind+0xb35/0x1a30 net/ipv6/af_inet6.c:340
 inet6_bind+0x206/0x300 net/ipv6/af_inet6.c:441
 kernel_bind+0xc6/0xf0 net/socket.c:3230
 udp_sock_create6+0x2ee/0x890 net/ipv6/ip6_udp_tunnel.c:39
 udp_sock_create include/net/udp_tunnel.h:61 [inline]
 tipc_udp_enable+0x166f/0x1d70 net/tipc/udp_media.c:742
 tipc_enable_bearer net/tipc/bearer.c:302 [inline]
 __tipc_nl_bearer_enable+0x1213/0x1da0 net/tipc/bearer.c:897
 tipc_nl_bearer_enable+0x6c/0xb0 net/tipc/bearer.c:905
 genl_family_rcv_msg net/netlink/genetlink.c:601 [inline]
 genl_rcv_msg+0x185f/0x1a60 net/netlink/genetlink.c:626
 netlink_rcv_skb+0x444/0x640 net/netlink/af_netlink.c:2477
 genl_rcv+0x63/0x80 net/netlink/genetlink.c:637
 netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
 netlink_unicast+0xf80/0x1060 net/netlink/af_netlink.c:1336
 netlink_sendmsg+0x129d/0x1310 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg net/socket.c:631 [inline]
 ___sys_sendmsg+0xdbc/0x11d0 net/socket.c:2116
 __sys_sendmsg net/socket.c:2154 [inline]
 __do_sys_sendmsg net/socket.c:2163 [inline]
 __se_sys_sendmsg+0x305/0x460 net/socket.c:2161
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2161
 do_syscall_64+0xcd/0x110 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x444199
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:00007ffe96b1eb28 EFLAGS: 00000213 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 0000000000444199
RDX: 0000000000000000 RSI: 00000000200008c0 RDI: 0000000000000003
RBP: 00000000006ce018 R08: 0000000000000000 R09: 00000000004002e0
R10: 0000000000000000 R11: 0000000000000213 R12: 0000000000401e40
R13: 0000000000401ed0 R14: 0000000000000000 R15: 0000000000000000

Local variable description: ----udp6_addr@udp_sock_create6
Variable was created at:
 udp_sock_create6+0x80/0x890 net/ipv6/ip6_udp_tunnel.c:17
 udp_sock_create include/net/udp_tunnel.h:61 [inline]
 tipc_udp_enable+0x166f/0x1d70 net/tipc/udp_media.c:742
==================================================================