sctp: pass a kernel pointer to sctp_setsockopt_hmac_ident

Use the kernel pointer that sctp_setsockopt has available instead of
directly handling the user pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -3565,13 +3565,11 @@ static int sctp_setsockopt_auth_chunk(struct sock *sk,
  * endpoint requires the peer to use.
  */
 static int sctp_setsockopt_hmac_ident(struct sock *sk,
-				      char __user *optval,
+				      struct sctp_hmacalgo *hmacs,
 				      unsigned int optlen)
 {
 	struct sctp_endpoint *ep = sctp_sk(sk)->ep;
-	struct sctp_hmacalgo *hmacs;
 	u32 idents;
-	int err;
 
 	if (!ep->auth_enable)
 		return -EACCES;
@@ -3581,21 +3579,12 @@ static int sctp_setsockopt_hmac_ident(struct sock *sk,
 	optlen = min_t(unsigned int, optlen, sizeof(struct sctp_hmacalgo) +
 					     SCTP_AUTH_NUM_HMACS * sizeof(u16));
 
-	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 ||
-	    (idents * sizeof(u16)) > (optlen - sizeof(struct sctp_hmacalgo))) {
-		err = -EINVAL;
-		goto out;
-	}
+	    (idents * sizeof(u16)) > (optlen - sizeof(struct sctp_hmacalgo)))
+		return -EINVAL;
 
-	err = sctp_auth_ep_set_hmacs(ep, hmacs);
-out:
-	kfree(hmacs);
-	return err;
+	return sctp_auth_ep_set_hmacs(ep, hmacs);
 }
 
 /*
@@ -4699,7 +4688,7 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,
 		retval = sctp_setsockopt_auth_chunk(sk, kopt, optlen);
 		break;
 	case SCTP_HMAC_IDENT:
-		retval = sctp_setsockopt_hmac_ident(sk, optval, optlen);
+		retval = sctp_setsockopt_hmac_ident(sk, kopt, optlen);
 		break;
 	case SCTP_AUTH_KEY:
 		retval = sctp_setsockopt_auth_key(sk, optval, optlen);