Fix memory errors

- `swaylock` does not free the password buffer on ENTER
 - read_line: OOB write when a line in /proc/modules contains a
   terminating character at `size` position.

common/readline.c

@@ -36,7 +36,7 @@ char *read_line(FILE *file) {
 		}
 		string[length++] = c;
 	}
-	if (length + 1 == size) {
+	if (length + 1 >= size) {
 		char *new_string = realloc(string, length + 1);
 		if (!new_string) {
 			free(string);

swaylock/main.c

@@ -172,6 +172,7 @@ void notify_key(enum wl_keyboard_key_state state, xkb_keysym_t sym, uint32_t cod
 			redraw_screen = 1;
 
 			password_size = 1024;
+			free(password);
 			password = malloc(password_size);
 			password[0] = '\0';
 			break;