Index: sys/compat/linux/linux_socket.c
===================================================================
--- sys/compat/linux/linux_socket.c	(revision 225919)
+++ sys/compat/linux/linux_socket.c	(working copy)
@@ -104,6 +104,7 @@
 	int oldv6size;
 	struct sockaddr_in6 *sin6;
 #endif
+	int namelen;
 
 	if (*osalen < 2 || *osalen > UCHAR_MAX || !osa)
 		return (EINVAL);
@@ -166,6 +167,20 @@
 		}
 	}
 
+	if ((bdom == AF_LOCAL) && (*osalen > sizeof(struct sockaddr_un))) {
+		for (namelen = 0;
+		    namelen < *osalen - offsetof(struct sockaddr_un, sun_path);
+		    namelen++)
+			if (!((struct sockaddr_un *)kosa)->sun_path[namelen])
+				break;
+		if (namelen + offsetof(struct sockaddr_un, sun_path) >
+		    sizeof(struct sockaddr_un)) {
+			error = EINVAL;
+			goto out;
+		}
+		alloclen = sizeof(struct sockaddr_un);
+	}
+
 	sa = (struct sockaddr *) kosa;
 	sa->sa_family = bdom;
 	sa->sa_len = alloclen;