netdev - [net] tipc: fix uninit-value in tipc_nl_node_reset_link

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Date:   Wed,  6 Jul 2022 10:47:52 +0700
From:   Hoang Le <hoang.h.le@...tech.com.au>
To:     jmaloy@...hat.com, maloy@...jonn.com, ying.xue@...driver.com,
        tung.q.nguyen@...tech.com.au, kuba@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com, tipc-discussion@...ts.sourceforge.net,
        netdev@...r.kernel.org, davem@...emloft.net
Cc:     syzbot+a73d24a22eeeebe5f244@...kaller.appspotmail.com
Subject: [net] tipc: fix uninit-value in tipc_nl_node_reset_link_stats

syzbot found the following issue on:
==================================================================
BUG: KMSAN: uninit-value in strlen lib/string.c:495 [inline]
BUG: KMSAN: uninit-value in strstr+0xb4/0x2e0 lib/string.c:840
 strlen lib/string.c:495 [inline]
 strstr+0xb4/0x2e0 lib/string.c:840
 tipc_nl_node_reset_link_stats+0x41e/0xba0 net/tipc/node.c:2582
 genl_family_rcv_msg_doit net/netlink/genetlink.c:731 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
 genl_rcv_msg+0x103f/0x1260 net/netlink/genetlink.c:792
 netlink_rcv_skb+0x3a5/0x6c0 net/netlink/af_netlink.c:2501
 genl_rcv+0x3c/0x50 net/netlink/genetlink.c:803
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0xf3b/0x1270 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x1288/0x1440 net/netlink/af_netlink.c:1921
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg net/socket.c:734 [inline]
 ____sys_sendmsg+0xabc/0xe90 net/socket.c:2492
 ___sys_sendmsg+0x2a5/0x350 net/socket.c:2546
 __sys_sendmsg net/socket.c:2575 [inline]
 __do_sys_sendmsg net/socket.c:2584 [inline]
 __se_sys_sendmsg net/socket.c:2582 [inline]
 __x64_sys_sendmsg+0x367/0x540 net/socket.c:2582
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
==================================================================

This is because link name string is not validated before it's used
in calling strstr() and strlen().

Reported-by: syzbot+a73d24a22eeeebe5f244@...kaller.appspotmail.com
Fixes: 03b6fefd9bb4 ("tipc: add support for broadcast rcv stats dumping")
Acked-by: Jon Maloy <jmaloy@...hat.com>
Signed-off-by: Hoang Le <hoang.h.le@...tech.com.au>
---
v2: remove redundant check
---
 net/tipc/node.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/tipc/node.c b/net/tipc/node.c
index b48d97cbbe29..80885780caa2 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -2574,8 +2574,10 @@ int tipc_nl_node_reset_link_stats(struct sk_buff *skb, struct genl_info *info)
 	if (!attrs[TIPC_NLA_LINK_NAME])
 		return -EINVAL;
 
-	link_name = nla_data(attrs[TIPC_NLA_LINK_NAME]);
+	if (nla_len(attrs[TIPC_NLA_LINK_NAME]) <= 0)
+		return -EINVAL;
 
+	link_name = nla_data(attrs[TIPC_NLA_LINK_NAME]);
 	err = -EINVAL;
 	if (!strcmp(link_name, tipc_bclink_name)) {
 		err = tipc_bclink_reset_stats(net, tipc_bc_sndlink(net));
-- 
2.30.2