diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index afa952e..9b9b2c3 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3144,7 +3144,7 @@
 		goto out;
 	}
 
-	if (authkey->sca_keylength > optlen) {
+	if (authkey->sca_keylength > optlen - sizeof(struct sctp_authkey)) {
 		ret = -EINVAL;
 		goto out;
 	}