From 83e70e1b6c7abd0315dd8cd5a98a91c58e0cd8bd Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Wed, 15 Jul 2020 16:43:26 -0400
Subject: munmap() extra pages during realloc()

---
 src/mapalloc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/mapalloc.c b/src/mapalloc.c
index afd8443..035332f 100644
--- a/src/mapalloc.c
+++ b/src/mapalloc.c
@@ -172,7 +172,12 @@ void *MA_realloc(void *ptr, size_t n)
 
 	if (n < (b->allocated - (PAGESIZE * 2))) {
 		b->used = n;
-		/* TODO: munmap() and mprotect() as necessary */
+		char *over = (char*)ptr + b->used + (PAGESIZE - (PAGESIZE % b->used));
+		if (over != b->over) {
+			mprotect(over, PAGESIZE, PROT_NONE);
+			munmap(over + PAGESIZE, (char*)b->over - over - PAGESIZE);
+			b->over = over;
+		}
 		return ptr;
 	}
 
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