Don't cheat: when only getting several bytes from each source, n is incremented

correctly, but RAND_add(..,n) counts the increasing n several times.
Only RAND_add(..,n) once entropy collection is finished.

crypto/rand/rand_unix.c

@@ -183,10 +183,13 @@ int RAND_poll(void)
 				&& t.tv_usec != 0 && n < ENTROPY_NEEDED);
 
 			close(fd);
-			RAND_add(tmpbuf,sizeof tmpbuf,n);
-			memset(tmpbuf,0,n);
 			}
 		}
+	if (n > 0)
+		{
+		RAND_add(tmpbuf,sizeof tmpbuf,n);
+		memset(tmpbuf,0,n);
+		}
 #endif
 
 	/* put in some default random data, we need more than just this */