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ref: e616d7aac9fff2d65bde4c6f8dcfc8d1222dc803
parent: 68f9fae973e2ffb6c0b9ed1e0761d3a0768455ad
author: Ben Harris <bjh21@bjh21.me.uk>
date: Sat Jan 7 15:33:42 EST 2023

Mosaic: fault out-of-bounds moves in execute_move()

Returning NULL in this case is better than dereferencing it.

--- a/mosaic.c
+++ b/mosaic.c
@@ -1297,6 +1297,10 @@
             return new_state;
         }
         cell = get_coords(new_state, new_state->cells_contents, x, y);
+        if (cell == NULL) {
+            sfree(new_state);
+            return NULL;
+        }
         if (*cell >= STATE_OK_NUM) {
             *cell &= STATE_OK_NUM;
         }
@@ -1363,6 +1367,10 @@
         for (i = 0; i < diff; i++) {
             cell = get_coords(new_state, new_state->cells_contents,
                               x + (dirX * i), y + (dirY * i));
+            if (cell == NULL) {
+                sfree(new_state);
+                return NULL;
+            }
             if ((*cell & STATE_OK_NUM) == 0) {
                 *cell = last_state;
                 update_board_state_around(new_state, x + (dirX * i),