diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 5cf39820d..4922d6120 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,8 @@
+2009-10-31  Corinna Vinschen  <corinna@vinschen.de>
+
+	* sec_helper.cc (security_descriptor::realloc): Call free first if
+	current security desriptor has been allocated by GetSecurityInfo.
+
 2009-10-30  Corinna Vinschen  <corinna@vinschen.de>
 
 	* sec_helper.cc (security_descriptor::free): If sd_size is 0, call
diff --git a/winsup/cygwin/sec_helper.cc b/winsup/cygwin/sec_helper.cc
index f8e01452f..755cab78f 100644
--- a/winsup/cygwin/sec_helper.cc
+++ b/winsup/cygwin/sec_helper.cc
@@ -288,6 +288,9 @@ security_descriptor::realloc (size_t nsize)
 {
   PSECURITY_DESCRIPTOR tmp;
 
+  /* Can't re-use buffer allocated by GetSecurityInfo. */
+  if (psd && !sd_size)
+    free ();
   if (!(tmp = (PSECURITY_DESCRIPTOR) ::realloc (psd, nsize)))
     return NULL;
   sd_size = nsize;