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
@@ -1,160 +1,163 @@
 /* ui-tree.c: functions for tree output
  *
  * Copyright (C) 2006 Lars Hjemli
  *
  * Licensed under GNU General Public License v2
  *   (see COPYING for full license text)
  */
 
 #include <ctype.h>
 #include "cgit.h"
 #include "html.h"
 #include "ui-shared.h"
 
 char *curr_rev;
 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;
         static char ascii[ROWLEN + 1];
 
         html("<table summary='blob content' class='bin-blob'>\n");
         html("<tr><th>ofs</th><th>hex dump</th><th>ascii</th></tr>");
         for (ofs = 0; ofs < size; ofs += ROWLEN, buf += ROWLEN) {
                 htmlf("<tr><td class='right'>%04x</td><td class='hex'>", ofs);
                 for (idx = 0; idx < ROWLEN && ofs + idx < size; idx++)
                         htmlf("%*s%02x",
                               idx == 16 ? 4 : 1, "",
                               buf[idx] & 0xff);
                 html(" </td><td class='hex'>");
                 for (idx = 0; idx < ROWLEN && ofs + idx < size; idx++)
                         ascii[idx] = isgraph(buf[idx]) ? buf[idx] : '.';
                 ascii[idx] = '\0';
                 html_txt(ascii);
                 html("</td></tr>\n");
         }
         html("</table>\n");
 }
 
 static void print_object(const unsigned char *sha1, char *path)
 {
         enum object_type type;
         char *buf;
         unsigned long size;
 
         type = sha1_object_info(sha1, &size);
         if (type == OBJ_BAD) {
                 cgit_print_error(fmt("Bad object name: %s",
                                      sha1_to_hex(sha1)));
                 return;
         }
 
         buf = read_sha1_file(sha1, &type, &size);
         if (!buf) {
                 cgit_print_error(fmt("Error reading object %s",
                                      sha1_to_hex(sha1)));
                 return;
         }
 
         html(" (");
         cgit_plain_link("plain", NULL, NULL, ctx.qry.head,
                         curr_rev, path);
         htmlf(")<br/>blob: %s\n", sha1_to_hex(sha1));
 
         if (buffer_is_binary(buf, size))
                 print_binary_buffer(buf, size);
         else
                 print_text_buffer(buf, size);
 }
 
 
 static int ls_item(const unsigned char *sha1, const char *base, int baselen,
                    const char *pathname, unsigned int mode, int stage,
                    void *cbdata)
 {
         char *name;
         char *fullpath;
         enum object_type type;
         unsigned long size = 0;
 
         name = xstrdup(pathname);
         fullpath = fmt("%s%s%s", ctx.qry.path ? ctx.qry.path : "",
                        ctx.qry.path ? "/" : "", name);
 
         if (!S_ISGITLINK(mode)) {
                 type = sha1_object_info(sha1, &size);
                 if (type == OBJ_BAD) {
                         htmlf("<tr><td colspan='3'>Bad object: %s %s</td></tr>",
                               name,
                               sha1_to_hex(sha1));
                         return 0;
                 }
         }
 
         html("<tr><td class='ls-mode'>");
         cgit_print_filemode(mode);
         html("</td><td>");
         if (S_ISGITLINK(mode)) {
                 htmlf("<a class='ls-mod' href='");
                 html_attr(fmt(ctx.repo->module_link,
                               name,
                               sha1_to_hex(sha1)));
                 html("'>");
                 html_txt(name);
                 html("</a>");
         } else if (S_ISDIR(mode)) {
                 cgit_tree_link(name, NULL, "ls-dir", ctx.qry.head,
                                curr_rev, fullpath);
         } else {
                 cgit_tree_link(name, NULL, "ls-blob", ctx.qry.head,
                                curr_rev, fullpath);
         }
         htmlf("</td><td class='ls-size'>%li</td>", size);
 
         html("<td>");
         cgit_log_link("log", NULL, "button", ctx.qry.head, curr_rev,
                       fullpath, 0, NULL, NULL, ctx.qry.showmsg);
         if (ctx.repo->max_stats)
                 cgit_stats_link("stats", NULL, "button", ctx.qry.head,
                                 fullpath);
         html("</td></tr>\n");
         free(name);
         return 0;
 }
 
 static void ls_head()
 {
         html("<table summary='tree listing' class='list'>\n");
         html("<tr class='nohover'>");
         html("<th class='left'>Mode</th>");
         html("<th class='left'>Name</th>");
         html("<th class='right'>Size</th>");
         html("<th/>");
         html("</tr>\n");
         header = 1;