Avoid potential crash at startup or in getgroups(2).

* grp.cc (internal_getgroups): Handle negative domain index to avoid
	crashes.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/ChangeLog

@@ -1,3 +1,8 @@
+2015-04-01  Corinna Vinschen  <corinna@vinschen.de>
+
+	* grp.cc (internal_getgroups): Handle negative domain index to avoid
+	crashes.
+
 2015-03-31  Renato Silva  <br.renatosilva@gmail.com>
 
 	* net.cc (cygwin_gethostname): Fix buffer size error handling.

winsup/cygwin/grp.cc

@@ -643,13 +643,17 @@ internal_getgroups (int gidsetsize, gid_t *grouplist, cyg_ldap *pldap)
 	{
 	  for (ULONG ncnt = 0; ncnt < scnt; ++ncnt)
 	    {
+	      static UNICODE_STRING empty = { 0, 0, (PWSTR) L"" };
 	      fetch_acc_t full_acc =
 		{
 		  .sid = sidp_buf[ncnt],
 		  .name = &nlst[ncnt].Name,
-		  .dom = &dlst->Domains[nlst[ncnt].DomainIndex].Name,
+		  .dom = &empty,
 		  .acc_type = nlst[ncnt].Use
 		};
+
+	      if (nlst[ncnt].DomainIndex >= 0)
+	        full_acc.dom = &dlst->Domains[nlst[ncnt].DomainIndex].Name;
 	      if ((grp = internal_getgrfull (full_acc, pldap)))
 		{
 		  if (cnt < gidsetsize)

winsup/cygwin/release/1.7.36

@@ -32,3 +32,6 @@ Bug Fixes
 - Avoid creating passwd and group records from fully qualified Windows
   account names (domain\name, name@domain).
   Addresses: https://cygwin.com/ml/cygwin/2015-03/msg00528.html
+
+- Avoid potential crash at startup or in getgroups(2).
+  Addresses: https://cygwin.com/ml/cygwin/2015-04/msg00010.html