inet_diag: Fix error path to cancel the meseage in inet_req_diag_fill()

stable inclusion
from linux-4.19.160
commit f0ec2cd03100ab287c9e5fce5ae56a76d6fc17a4

--------------------------------

[ Upstream commit e33de7c5 ]

nlmsg_cancel() needs to be called in the error path of
inet_req_diag_fill to cancel the message.

Fixes: d545caca ("net: inet: diag: expose the socket mark to privileged processes.")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NWang Hai <wanghai38@huawei.com>
Link: https://lore.kernel.org/r/20201116082018.16496-1-wanghai38@huawei.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

net/ipv4/inet_diag.c

@@ -392,8 +392,10 @@ static int inet_req_diag_fill(struct sock *sk, struct sk_buff *skb,
 	r->idiag_inode	= 0;
 
 	if (net_admin && nla_put_u32(skb, INET_DIAG_MARK,
-				     inet_rsk(reqsk)->ir_mark))
+				     inet_rsk(reqsk)->ir_mark)) {
+		nlmsg_cancel(skb, nlh);
 		return -EMSGSIZE;
+	}
 
 	nlmsg_end(skb, nlh);
 	return 0;