tipc: Change nla_policy for bearer-related names to NLA_NUL_STRING

In the Linux kernel, the following vulnerability has been resolved:

tipc: Change nla_policy for bearer-related names to NLA_NUL_STRING

syzbot reported the following uninit-value access issue [1]:

=====================================================
BUG: KMSAN: uninit-value in strlen lib/string.c:418 [inline]
BUG: KMSAN: uninit-value in strstr+0xb8/0x2f0 lib/string.c:756
strlen lib/string.c:418 [inline]
strstr+0xb8/0x2f0 lib/string.c:756
tipc_nl_node_reset_link_stats+0x3ea/0xb50 net/tipc/node.c:2595
genl_family_rcv_msg_doit net/netlink/genetlink.c:971 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:1051 [inline]
genl_rcv_msg+0x11ec/0x1290 net/netlink/genetlink.c:1066
netlink_rcv_skb+0x371/0x650 net/netlink/af_netlink.c:2545
genl_rcv+0x40/0x60 net/netlink/genetlink.c:1075
netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline]
netlink_unicast+0xf47/0x1250 net/netlink/af_netlink.c:1368
netlink_sendmsg+0x1238/0x13d0 net/netlink/af_netlink.c:1910
sock_sendmsg_nosec net/socket.c:730 [inline]
sock_sendmsg net/socket.c:753 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2541
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2595
__sys_sendmsg net/socket.c:2624 [inline]
__do_sys_sendmsg net/socket.c:2633 [inline]
__se_sys_sendmsg net/socket.c:2631 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2631
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Uninit was created at:
slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
slab_alloc_node mm/slub.c:3478 [inline]
kmem_cache_alloc_node+0x577/0xa80 mm/slub.c:3523
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:559
__alloc_skb+0x318/0x740 net/core/skbuff.c:650
alloc_skb include/linux/skbuff.h:1286 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1214 [inline]
netlink_sendmsg+0xb34/0x13d0 net/netlink/af_netlink.c:1885
sock_sendmsg_nosec net/socket.c:730 [inline]
sock_sendmsg net/socket.c:753 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2541
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2595
__sys_sendmsg net/socket.c:2624 [inline]
__do_sys_sendmsg net/socket.c:2633 [inline]
__se_sys_sendmsg net/socket.c:2631 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2631
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

TIPC bearer-related names including link names must be null-terminated
strings. If a link name which is not null-terminated is passed through
netlink, strstr() and similar functions can cause buffer overrun. This
causes the above issue.

This patch changes the nla_policy for bearer-related names from NLA_STRING
to NLA_NUL_STRING. This resolves the issue by ensuring that only
null-terminated strings are accepted as bearer-related names.

syzbot reported similar uninit-value issue related to bearer names [2]. The
root cause of this issue is that a non-null-terminated bearer name was
passed. This patch also resolved this issue.