[newlib-cygwin] Allocate temporary TOKEN_GROUP arrays using TLS

[Corinna Vinschen <corinna at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=155a1ec5fb27dcbbc2e6464bc6e5d8b08c0b03e5

commit 155a1ec5fb27dcbbc2e6464bc6e5d8b08c0b03e5
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Wed Mar 23 17:40:24 2016 +0100

    Allocate temporary TOKEN_GROUP arrays using TLS
    
    A user token can be up to 64K in size.  The group list might take a lot
    of that so use tmp_pathbuf allocated space rather than stack space
    allocted via alloca.  In create_token the TOKEN_GROUP was allocated via
    malloc, but the code is needlessly complicated.  Simplify by using
    tmp_pathbuf as well.
    
    	* sec_auth.cc (verify_token): Allocate TOKEN_GROUP via tmp_pathbuf.
    	(create_token): Ditto.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/sec_auth.cc | 40 ++++++++++++----------------------------
 1 file changed, 12 insertions(+), 28 deletions(-)

diff --git a/winsup/cygwin/sec_auth.cc b/winsup/cygwin/sec_auth.cc
index ba29339..b6dc9d6 100644
--- a/winsup/cygwin/sec_auth.cc
+++ b/winsup/cygwin/sec_auth.cc
@@ -763,6 +763,7 @@ verify_token (HANDLE token, cygsid &usersid, user_groups &groups, bool *pintern)
   NTSTATUS status;
   ULONG size;
   bool intern = false;
+  tmp_pathbuf tp;
 
   if (pintern)
     {
@@ -808,16 +809,10 @@ verify_token (HANDLE token, cygsid &usersid, user_groups &groups, bool *pintern)
 	return gsid == groups.pgsid;
     }
 
-  PTOKEN_GROUPS my_grps;
+  PTOKEN_GROUPS my_grps = (PTOKEN_GROUPS) tp.w_get ();
 
-  status = NtQueryInformationToken (token, TokenGroups, NULL, 0, &size);
-  if (!NT_SUCCESS (status) && status != STATUS_BUFFER_TOO_SMALL)
-    {
-      debug_printf ("NtQueryInformationToken(token, TokenGroups), %y", status);
-      return false;
-    }
-  my_grps = (PTOKEN_GROUPS) alloca (size);
-  status = NtQueryInformationToken (token, TokenGroups, my_grps, size, &size);
+  status = NtQueryInformationToken (token, TokenGroups, my_grps,
+				    2 * NT_MAX_PATH, &size);
   if (!NT_SUCCESS (status))
     {
       debug_printf ("NtQueryInformationToken(my_token, TokenGroups), %y",
@@ -903,6 +898,7 @@ create_token (cygsid &usersid, user_groups &new_groups)
   HANDLE token = INVALID_HANDLE_VALUE;
   HANDLE primary_token = INVALID_HANDLE_VALUE;
 
+  tmp_pathbuf tp;
   PTOKEN_GROUPS my_tok_gsids = NULL;
   cygpsid mandatory_integrity_sid;
   ULONG size;
@@ -938,24 +934,14 @@ create_token (cygsid &usersid, user_groups &new_groups)
 
       /* Retrieving current processes group list to be able to inherit
 	 some important well known group sids. */
-      status = NtQueryInformationToken (hProcToken, TokenGroups, NULL, 0,
-					&size);
-      if (!NT_SUCCESS (status) && status != STATUS_BUFFER_TOO_SMALL)
-	debug_printf ("NtQueryInformationToken(hProcToken, TokenGroups), %y",
-		      status);
-      else if (!(my_tok_gsids = (PTOKEN_GROUPS) malloc (size)))
-	debug_printf ("malloc (my_tok_gsids) failed.");
-      else
+      my_tok_gsids = (PTOKEN_GROUPS) tp.w_get ();
+      status = NtQueryInformationToken (hProcToken, TokenGroups, my_tok_gsids,
+					2 * NT_MAX_PATH, &size);
+      if (!NT_SUCCESS (status))
 	{
-	  status = NtQueryInformationToken (hProcToken, TokenGroups,
-					    my_tok_gsids, size, &size);
-	  if (!NT_SUCCESS (status))
-	    {
-	      debug_printf ("NtQueryInformationToken(hProcToken, TokenGroups), "
-			    "%y", status);
-	      free (my_tok_gsids);
-	      my_tok_gsids = NULL;
-	    }
+	  debug_printf ("NtQueryInformationToken(hProcToken, TokenGroups), "
+			"%y", status);
+	  my_tok_gsids = NULL;
 	}
     }
 
@@ -1022,8 +1008,6 @@ out:
     CloseHandle (token);
   if (privs)
     free (privs);
-  if (my_tok_gsids)
-    free (my_tok_gsids);
   lsa_close_policy (lsa);
 
   debug_printf ("%p = create_token ()", primary_token);