builtin/help: fix dangling reference to html_path

In `get_html_page_path()` we may end up assigning the return value of
`system_path()` to the global `html_path` variable. But as we also
assign the returned value to `to_free`, we will deallocate its memory
upon returning from the function. Consequently, `html_path` will now
point to deallocated memory.

Fix this issue by instead assigning the value to a separate local
variable.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

builtin/help.c

@@ -513,23 +513,24 @@ static void show_info_page(const char *page)
 static void get_html_page_path(struct strbuf *page_path, const char *page)
 {
 	struct stat st;
+	const char *path = html_path;
 	char *to_free = NULL;
 
-	if (!html_path)
-		html_path = to_free = system_path(GIT_HTML_PATH);
+	if (!path)
+		path = to_free = system_path(GIT_HTML_PATH);
 
 	/*
 	 * Check that the page we're looking for exists.
 	 */
-	if (!strstr(html_path, "://")) {
-		if (stat(mkpath("%s/%s.html", html_path, page), &st)
+	if (!strstr(path, "://")) {
+		if (stat(mkpath("%s/%s.html", path, page), &st)
 		    || !S_ISREG(st.st_mode))
 			die("'%s/%s.html': documentation file not found.",
-				html_path, page);
+				path, page);
 	}
 
 	strbuf_init(page_path, 0);
-	strbuf_addf(page_path, "%s/%s.html", html_path, page);
+	strbuf_addf(page_path, "%s/%s.html", path, page);
 	free(to_free);
 }