crypto: user - fix memory leak in crypto_report

CVE-2019-19062

In crypto_report, a new skb is created via nlmsg_new(). This skb should
be released if crypto_report_alg() fails.

Fixes: a38f7907 ("crypto: Add userspace configuration API")
Cc: <stable@vger.kernel.org>
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
(backported from commit ffdde593)
[PHLin: crypto_user.c not renamed yet, backported with the same logic]
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Connor Kuehl <connor.kuehl@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

crypto/crypto_user.c

@@ -269,8 +269,10 @@ static int crypto_report(struct sk_buff *in_skb, struct nlmsghdr *in_nlh,
 drop_alg:
 	crypto_mod_put(alg);
 
-	if (err)
+	if (err) {
+		kfree_skb(skb);
 		return err;
+	}
 
 	return nlmsg_unicast(crypto_nlsk, skb, NETLINK_CB(in_skb).portid);
 }