sctp: pass a kernel pointer to sctp_setsockopt_adaptation_layer

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

@@ -3336,17 +3336,14 @@ static int sctp_setsockopt_peer_primary_addr(struct sock *sk,
 	return err;
 }
 
-static int sctp_setsockopt_adaptation_layer(struct sock *sk, char __user *optval,
+static int sctp_setsockopt_adaptation_layer(struct sock *sk,
+					    struct sctp_setadaptation *adapt,
 					    unsigned int optlen)
 {
-	struct sctp_setadaptation adaptation;
-
 	if (optlen != sizeof(struct sctp_setadaptation))
 		return -EINVAL;
-	if (copy_from_user(&adaptation, optval, optlen))
-		return -EFAULT;
 
-	sctp_sk(sk)->adaptation_ind = adaptation.ssb_adaptation_ind;
+	sctp_sk(sk)->adaptation_ind = adapt->ssb_adaptation_ind;
 
 	return 0;
 }
@@ -4700,7 +4697,7 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,
 		retval = sctp_setsockopt_maxseg(sk, kopt, optlen);
 		break;
 	case SCTP_ADAPTATION_LAYER:
-		retval = sctp_setsockopt_adaptation_layer(sk, optval, optlen);
+		retval = sctp_setsockopt_adaptation_layer(sk, kopt, optlen);
 		break;
 	case SCTP_CONTEXT:
 		retval = sctp_setsockopt_context(sk, optval, optlen);