Re: [Bug-tar] Re: [Bug-cpio] [PATCH] lib/paxnames.c: Do not use alloca to avoid stack overflow

[Sergey Poznyakoff]

Dmitry V. Levin <address@hidden> ha escrit:

> I do not suggest to remove xstrdup completely, just replace it with
> xmalloc; nothing more, nothing less.

Yes, indeed, I misread it. Thanks for pointing that out. I have
installed the following patch: 

Index: paxlib/names.c
===================================================================
RCS file: /cvsroot/paxutils/paxutils/paxlib/names.c,v
retrieving revision 1.2
diff -p -u -r1.2 names.c
--- paxlib/names.c      27 Jun 2007 13:49:33 -0000      1.2
+++ paxlib/names.c      17 Aug 2007 11:35:04 -0000
@@ -36,15 +36,27 @@ hash_string_compare (void const *name1, 
   return strcmp (name1, name2) == 0;
 }
 
-/* Return zero if TABLE contains a copy of STRING; otherwise, insert a
-   copy of STRING to TABLE and return 1.  */
-bool
-hash_string_insert (Hash_table **table, char const *string)
+/* Return zero if TABLE contains a LEN-character long prefix of STRING,
+   otherwise, insert a newly allocated copy of this prefix to TABLE and
+   return 1.  If RETURN_PREFIX is not NULL, point it to the allocated
+   copy. */
+static bool
+hash_string_insert_prefix (Hash_table **table, char const *string, size_t len,
+                          const char **return_prefix)
 {
   Hash_table *t = *table;
-  char *s = xstrdup (string);
+  char *s;
   char *e;
 
+  if (len)
+    {
+      s = xmalloc (len + 1);
+      memcpy (s, string, len);
+      s[len] = 0;
+    }
+  else
+    s = xstrdup (string);
+  
   if (! ((t
          || (*table = t = hash_initialize (0, 0, hash_string_hasher,
                                            hash_string_compare, 0)))
@@ -52,7 +64,11 @@ hash_string_insert (Hash_table **table, 
     xalloc_die ();
 
   if (e == s)
-    return 1;
+    {
+      if (return_prefix)
+       *return_prefix = s;
+      return 1;
+    }
   else
     {
       free (s);
@@ -60,6 +76,14 @@ hash_string_insert (Hash_table **table, 
     }
 }
 
+/* Return zero if TABLE contains a copy of STRING; otherwise, insert a
+   copy of STRING to TABLE and return 1.  */
+bool
+hash_string_insert (Hash_table **table, char const *string)
+{
+  return hash_string_insert_prefix (table, string, 0, NULL);
+}
+
 /* Return 1 if TABLE contains STRING.  */
 bool
 hash_string_lookup (Hash_table const *table, char const *string)
@@ -88,7 +112,8 @@ removed_prefixes_p (void)
    If ABSOLUTE_NAMES is 0, strip filesystem prefix from the file name. */
 
 char *
-safer_name_suffix (char const *file_name, bool link_target, bool 
absolute_names)
+safer_name_suffix (char const *file_name, bool link_target,
+                  bool absolute_names)
 {
   char const *p;
 
@@ -121,11 +146,9 @@ safer_name_suffix (char const *file_name
 
       if (prefix_len)
        {
-         char *prefix = alloca (prefix_len + 1);
-         memcpy (prefix, file_name, prefix_len);
-         prefix[prefix_len] = '\0';
-
-         if (hash_string_insert (&prefix_table[link_target], prefix))
+         const char **prefix;
+         if (hash_string_insert_prefix (&prefix_table[link_target], file_name,
+                                        prefix_len, &prefix))
            {
              static char const *const diagnostic[] =
              {


Regards,
Sergey