From 91735e5019be84d2fa693c5d40746c818ace28f8 Mon Sep 17 00:00:00 2001
From: Ben Harris <bjh21@bjh21.me.uk>
Date: Fri, 31 Mar 2023 20:38:31 +0100
Subject: [PATCH] Correct a range check in Magnets' layout verification

Squares in the grid are numbered from 0, so the upper limit check
needs to use "<=" rather than "<".  Without this, invalid descriptions
can cause a read overrun off the end of the board.
---
 magnets.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/magnets.c b/magnets.c
index d190848..d95d146 100644
--- a/magnets.c
+++ b/magnets.c
@@ -520,7 +520,7 @@ nextchar:
      * (i.e. each end points to the other) */
     for (idx = 0; idx < state->wh; idx++) {
         if (state->common->dominoes[idx] < 0 ||
-            state->common->dominoes[idx] > state->wh ||
+            state->common->dominoes[idx] >= state->wh ||
             state->common->dominoes[state->common->dominoes[idx]] != idx) {
             *prob = "Domino descriptions inconsistent";
             goto done;