estream: Fix unclean usage of realloc.

* common/estream-printf.c (_ESTREAM_PRINTF_MALLOC): Remove.
(_ESTREAM_PRINTF_FREE): Remove.
(_ESTREAM_PRINTF_REALLOC): New.
(fixed_realloc) [!_ESTREAM_PRINTF_REALLOC]): New.
(estream_vasprintf): Use my_printf_realloc instead of my_printf_malloc
and my_printf_free.
(dynamic_buffer_out): Use my_printf_realloc instead of realloc.
--

This bug will never happen in current GnuPG/Libgcrypt because we use
the standard memory allocation functions via Libgcrypt.  However, when
used in other environments it would mess up the heap for an asprintf
with an output length larger than ~512 bytes.

1 files changed, 29 insertions, 13 deletions

diff --git a/common/estream-printf.c b/common/estream-printf.c
index 848ff0301..e50eb7c05 100644
--- a/common/estream-printf.c
+++ b/common/estream-printf.c
@@ -1,5 +1,5 @@
 /* estream-printf.c - Versatile mostly C-99 compliant printf formatting
- * Copyright (C) 2007, 2008, 2009, 2010 g10 Code GmbH
+ * Copyright (C) 2007, 2008, 2009, 2010, 2012 g10 Code GmbH
  *
  * This file is part of Libestream.
  *
@@ -109,16 +109,11 @@
 /* #define DEBUG 1 */
 
 
-/* Allow redefinition of asprintf used malloc functions.  */
-#if defined(_ESTREAM_PRINTF_MALLOC)
-#define my_printf_malloc(a) _ESTREAM_PRINTF_MALLOC((a))
+/* Allow redefinition of asprintf used realloc function.  */
+#if defined(_ESTREAM_PRINTF_REALLOC)
+#define my_printf_realloc(a,b) _ESTREAM_PRINTF_REALLOC((a),(b))
 #else
-#define my_printf_malloc(a) malloc((a))
-#endif
-#if defined(_ESTREAM_PRINTF_FREE)
-#define my_printf_free(a)   _ESTREAM_PRINTF_FREE((a))
-#else
-#define my_printf_free(a)   free((a))
+#define my_printf_realloc(a,b) fixed_realloc((a),(b))
 #endif
 
 /* A wrapper to set ERRNO.  */
@@ -309,6 +304,26 @@ struct valueitem_s
 };
 typedef struct valueitem_s *valueitem_t;
 
+
+/* Not all systems have a C-90 compliant realloc.  To cope with this
+   we use this simple wrapper. */
+#ifndef _ESTREAM_PRINTF_REALLOC
+static void *
+fixed_realloc (void *a, size_t n)
+{
+  if (!a)
+    return malloc (n);
+
+  if (!n)
+    {
+      free (a);
+      return NULL;
+    }
+
+  return realloc (a, n);
+}
+#endif /*!_ESTREAM_PRINTF_REALLOC*/
+
 
 #ifdef DEBUG
 static void
@@ -1762,7 +1777,7 @@ dynamic_buffer_out (void *outfncarg, const char *buf, size_t buflen)
       char *p;
 
       parm->alloced += buflen + 512;
-      p = realloc (parm->buffer, parm->alloced);
+      p = my_printf_realloc (parm->buffer, parm->alloced);
       if (!p)
         {
           parm->error_flag = errno ? errno : ENOMEM;
@@ -1792,7 +1807,7 @@ estream_vasprintf (char **bufp, const char *format, va_list arg_ptr)
   parm.error_flag = 0;
   parm.alloced = 512;
   parm.used = 0;
-  parm.buffer = my_printf_malloc (parm.alloced);
+  parm.buffer = my_printf_realloc (NULL, parm.alloced);
   if (!parm.buffer)
     {
       *bufp = NULL;
@@ -1811,7 +1826,8 @@ estream_vasprintf (char **bufp, const char *format, va_list arg_ptr)
   if (rc == -1)
     {
       memset (parm.buffer, 0, parm.used);
-      my_printf_free (parm.buffer);
+      if (parm.buffer)
+        my_printf_realloc (parm.buffer, 0);
       *bufp = NULL;
       return -1;
     }