sctp: pass a kernel pointer to sctp_setsockopt_auth_chunk

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

@@ -3535,21 +3535,18 @@ static int sctp_setsockopt_maxburst(struct sock *sk,
  * will only effect future associations on the socket.
  */
 static int sctp_setsockopt_auth_chunk(struct sock *sk,
-				      char __user *optval,
+				      struct sctp_authchunk *val,
 				      unsigned int optlen)
 {
 	struct sctp_endpoint *ep = sctp_sk(sk)->ep;
-	struct sctp_authchunk val;
 
 	if (!ep->auth_enable)
 		return -EACCES;
 
 	if (optlen != sizeof(struct sctp_authchunk))
 		return -EINVAL;
-	if (copy_from_user(&val, optval, optlen))
-		return -EFAULT;
 
-	switch (val.sauth_chunk) {
+	switch (val->sauth_chunk) {
 	case SCTP_CID_INIT:
 	case SCTP_CID_INIT_ACK:
 	case SCTP_CID_SHUTDOWN_COMPLETE:
@@ -3558,7 +3555,7 @@ static int sctp_setsockopt_auth_chunk(struct sock *sk,
 	}
 
 	/* add this chunk id to the endpoint */
-	return sctp_auth_ep_add_chunkid(ep, val.sauth_chunk);
+	return sctp_auth_ep_add_chunkid(ep, val->sauth_chunk);
 }
 
 /*
@@ -4699,7 +4696,7 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,
 		retval = sctp_setsockopt_maxburst(sk, kopt, optlen);
 		break;
 	case SCTP_AUTH_CHUNK:
-		retval = sctp_setsockopt_auth_chunk(sk, optval, optlen);
+		retval = sctp_setsockopt_auth_chunk(sk, kopt, optlen);
 		break;
 	case SCTP_HMAC_IDENT:
 		retval = sctp_setsockopt_hmac_ident(sk, optval, optlen);