From c693be47f8f39f50f045c48254c79e59c2b74830 Mon Sep 17 00:00:00 2001
From: toaster <rollerorbital@gmail.com>
Date: Wed, 14 Dec 2022 17:30:39 +0000
Subject: [PATCH] Fix possible out of bounds memory access for M_MapLocked

---
 src/m_cond.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/m_cond.c b/src/m_cond.c
index 67a8733cc..de31176ea 100644
--- a/src/m_cond.c
+++ b/src/m_cond.c
@@ -1099,6 +1099,9 @@ boolean M_MapLocked(INT32 mapnum)
 	// No skipping over any part of your marathon.
 	if (marathonmode)
 		return false;
+
+	if (!mapnum || mapnum > nummapheaders)
+		return false;
 	
 	if (!mapheaderinfo[mapnum-1])
 		return false;