sctp: use memdup_user to copy data from userspace

Use common function to simply code.
Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -3215,14 +3215,9 @@ static int sctp_setsockopt_hmac_ident(struct sock *sk,
 	if (optlen < sizeof(struct sctp_hmacalgo))
 		return -EINVAL;
 
-	hmacs = kmalloc(optlen, GFP_KERNEL);
-	if (!hmacs)
-		return -ENOMEM;
-
-	if (copy_from_user(hmacs, optval, optlen)) {
-		err = -EFAULT;
-		goto out;
-	}
+	hmacs= memdup_user(optval, optlen);
+	if (IS_ERR(hmacs))
+		return PTR_ERR(hmacs);
 
 	idents = hmacs->shmac_num_idents;
 	if (idents == 0 || idents > SCTP_AUTH_NUM_HMACS ||
@@ -3257,14 +3252,9 @@ static int sctp_setsockopt_auth_key(struct sock *sk,
 	if (optlen <= sizeof(struct sctp_authkey))
 		return -EINVAL;
 
-	authkey = kmalloc(optlen, GFP_KERNEL);
-	if (!authkey)
-		return -ENOMEM;
-
-	if (copy_from_user(authkey, optval, optlen)) {
-		ret = -EFAULT;
-		goto out;
-	}
+	authkey= memdup_user(optval, optlen);
+	if (IS_ERR(authkey))
+		return PTR_ERR(authkey);
 
 	if (authkey->sca_keylength > optlen - sizeof(struct sctp_authkey)) {
 		ret = -EINVAL;