From: Fletcher T. Penney <fletcher@fletcherpenney.net>
Date: Sun, 11 Mar 2018 14:11:21 +0000 (-0400)
Subject: FIXED: Fix detection of invalid request to copy substring of DString
X-Git-Tag: 6.3.1^2~10
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=fad24da388169c8c54f89802b8845ea33bd973c4;p=multimarkdown

FIXED: Fix detection of invalid request to copy substring of DString
---

diff --git a/Sources/libMultiMarkdown/d_string.c b/Sources/libMultiMarkdown/d_string.c
index 036cce4..9442f1b 100644
--- a/Sources/libMultiMarkdown/d_string.c
+++ b/Sources/libMultiMarkdown/d_string.c
@@ -650,17 +650,21 @@ char * d_string_copy_substring(DString * d, size_t start, size_t len) {
 	if (d) {
 		char * result;
 
-		if ((len == -1) && (start < d->currentStringLength)) {
-			len = d->currentStringLength - start;
-		} else {
-			if (start + len > d->currentStringLength) {
-				fprintf(stderr, "d_string: Asked to copy invalid substring range.\n");
-				fprintf(stderr, "start: %lu  len: %lu  string: %lu\n", start, len,
-						d->currentStringLength);
-				return NULL;
+		if (len == -1) {
+			if (start <= d->currentStringLength) {
+				len = d->currentStringLength - start;
+			} else {
+				len = 0;
 			}
 		}
 
+		if (start + len > d->currentStringLength) {
+			fprintf(stderr, "d_string: Asked to copy invalid substring range.\n");
+			fprintf(stderr, "start: %lu  len: %lu  string: %lu\n", start, len,
+					d->currentStringLength);
+			return NULL;
+		}
+
 		result = malloc(len + 1);
 		strncpy(result, &d->str[start], len);
 		result[len] = '\0';