fix segfault when displaying empty blobs

When size is zero, subtracting one from it turns it into
ULONG_MAX which causes an out-of-bounds access on buf.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/ui-tree.c b/ui-tree.c
index c6159ec..553dbaa 100644
--- a/ui-tree.c
+++ b/ui-tree.c
@@ -16,29 +16,32 @@ char *match_path;
 int header = 0;
 
 static void print_text_buffer(char *buf, unsigned long size)
 {
 	unsigned long lineno, idx;
 	const char *numberfmt =
 		"<a class='no' id='n%1$d' name='n%1$d' href='#n%1$d'>%1$d</a>\n";
 
 	html("<table summary='blob content' class='blob'>\n");
 	html("<tr><td class='linenumbers'><pre>");
 	idx = 0;
 	lineno = 0;
-	htmlf(numberfmt, ++lineno);
-	while(idx < size - 1) { // skip absolute last newline
-		if (buf[idx] == '\n')
-			htmlf(numberfmt, ++lineno);
-		idx++;
+
+	if (size) {
+		htmlf(numberfmt, ++lineno);
+		while(idx < size - 1) { // skip absolute last newline
+			if (buf[idx] == '\n')
+				htmlf(numberfmt, ++lineno);
+			idx++;
+		}
 	}
 	html("</pre></td>\n");
 	html("<td class='lines'><pre><code>");
 	html_txt(buf);
 	html("</code></pre></td></tr></table>\n");
 }
 
 #define ROWLEN 32
 
 static void print_binary_buffer(char *buf, unsigned long size)
 {
 	unsigned long ofs, idx;