001-Protect-array_list_del_idx-against-size_t-overflow.patch

From 099016b7e8d70a6d5dd814e788bba08d33d48426 Mon Sep 17 00:00:00 2001
From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Mon, 4 May 2020 19:41:16 +0200
Subject: [PATCH 1/2] Protect array_list_del_idx against size_t overflow.

If the assignment of stop overflows due to idx and count being
larger than SIZE_T_MAX in sum, out of boundary access could happen.

It takes invalid usage of this function for this to happen, but
I decided to add this check so array_list_del_idx is as safe against
bad usage as the other arraylist functions.
---
 arraylist.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/arraylist.c
+++ b/arraylist.c
@@ -135,6 +135,9 @@ array_list_del_idx( struct array_list *a
 {
 	size_t i, stop;
 
+	/* Avoid overflow in calculation with large indices. */
+	if (idx > SIZE_T_MAX - count)
+		return -1;
 	stop = idx + count;
 	if ( idx >= arr->length || stop > arr->length ) return -1;
 	for ( i = idx; i < stop; ++i ) {