CVE-2023-52845: tipc: Change nla_policy for bearer-related names to NLA_NUL_STRING

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

tipc: Change nlapolicy for bearer-related names to NLANULSTRING

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 tipcnlnoderesetlinkstats+0x3ea/0xb50 net/tipc/node.c:2595 genlfamilyrcvmsgdoit net/netlink/genetlink.c:971 [inline] genlfamilyrcvmsg net/netlink/genetlink.c:1051 [inline] genlrcvmsg+0x11ec/0x1290 net/netlink/genetlink.c:1066 netlinkrcvskb+0x371/0x650 net/netlink/afnetlink.c:2545 genlrcv+0x40/0x60 net/netlink/genetlink.c:1075 netlinkunicastkernel net/netlink/afnetlink.c:1342 [inline] netlinkunicast+0xf47/0x1250 net/netlink/afnetlink.c:1368 netlinksendmsg+0x1238/0x13d0 net/netlink/afnetlink.c:1910 socksendmsgnosec net/socket.c:730 [inline] socksendmsg net/socket.c:753 [inline] syssendmsg+0x9c2/0xd60 net/socket.c:2541 syssendmsg+0x28d/0x3c0 net/socket.c:2595 syssendmsg net/socket.c:2624 [inline] dosyssendmsg net/socket.c:2633 [inline] sesyssendmsg net/socket.c:2631 [inline] x64syssendmsg+0x307/0x490 net/socket.c:2631 dosyscallx64 arch/x86/entry/common.c:50 [inline] dosyscall64+0x41/0xc0 arch/x86/entry/common.c:80 entrySYSCALL64afterhwframe+0x63/0xcd

Uninit was created at: slabpostallochook+0x12f/0xb70 mm/slab.h:767 slaballocnode mm/slub.c:3478 [inline] kmemcacheallocnode+0x577/0xa80 mm/slub.c:3523 kmallocreserve+0x13d/0x4a0 net/core/skbuff.c:559 allocskb+0x318/0x740 net/core/skbuff.c:650 allocskb include/linux/skbuff.h:1286 [inline] netlinkalloclargeskb net/netlink/afnetlink.c:1214 [inline] netlinksendmsg+0xb34/0x13d0 net/netlink/afnetlink.c:1885 socksendmsgnosec net/socket.c:730 [inline] socksendmsg net/socket.c:753 [inline] syssendmsg+0x9c2/0xd60 net/socket.c:2541 syssendmsg+0x28d/0x3c0 net/socket.c:2595 syssendmsg net/socket.c:2624 [inline] dosyssendmsg net/socket.c:2633 [inline] sesyssendmsg net/socket.c:2631 [inline] x64syssendmsg+0x307/0x490 net/socket.c:2631 dosyscallx64 arch/x86/entry/common.c:50 [inline] dosyscall64+0x41/0xc0 arch/x86/entry/common.c:80 entrySYSCALL64afterhwframe+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 nlapolicy for bearer-related names from NLASTRING to NLANULSTRING. 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.