crypto: user - no parsing of CRYPTO_MSG_GETALG

The CRYPTO_MSG_GETALG netlink message type provides a buffer to the
kernel to retrieve information from the kernel. The data buffer will not
provide any input and will not be read. Hence the nlmsg_parse is not
applicable to this netlink message type.

This patch fixes the following kernel log message when using this
netlink interface:

netlink: 208 bytes leftover after parsing attributes in process `XXX'.

Patch successfully tested with libkcapi from [1] which uses
CRYPTO_MSG_GETALG to obtain cipher-specific information from the kernel.

[1] http://www.chronox.de/libkcapi.html

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/crypto_user.c

@@ -516,10 +516,12 @@ static int crypto_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 		return err;
 	}
 
-	err = nlmsg_parse(nlh, crypto_msg_min[type], attrs, CRYPTOCFGA_MAX,
-			  crypto_policy);
-	if (err < 0)
-		return err;
+	if (type != (CRYPTO_MSG_GETALG - CRYPTO_MSG_BASE)) {
+		err = nlmsg_parse(nlh, crypto_msg_min[type], attrs,
+				  CRYPTOCFGA_MAX, crypto_policy);
+		if (err < 0)
+			return err;
+	}
 
 	if (link->doit == NULL)
 		return -EINVAL;