From 5fec7b777f4a0beb0512fcbdb71cc3a132631ac8 Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@openldap.org>
Date: Thu, 11 Jul 2019 14:18:37 +0100
Subject: [PATCH] ITS#8977 don't use any stack allocated IDLs

Trying again, fixed previous attempt
---
 servers/slapd/back-mdb/search.c | 48 ++++++++++++++++++++++++---------
 1 file changed, 36 insertions(+), 12 deletions(-)

diff --git a/servers/slapd/back-mdb/search.c b/servers/slapd/back-mdb/search.c
index 153c2d3916..1bfd0bc29c 100644
--- a/servers/slapd/back-mdb/search.c
+++ b/servers/slapd/back-mdb/search.c
@@ -416,8 +416,7 @@ mdb_search( Operation *op, SlapReply *rs )
 	struct mdb_info *mdb = (struct mdb_info *) op->o_bd->be_private;
 	ID		id, cursor, nsubs, ncand, cscope;
 	ID		lastid = NOID;
-	ID		candidates[MDB_idl_um_size];
-	ID		iscopes[MDB_idl_db_size];
+	ID		*candidates, *iscopes, *c0;
 	ID2		*scopes;
 	void	*stack;
 	Entry		*e = NULL, *base = NULL;
@@ -465,7 +464,14 @@ mdb_search( Operation *op, SlapReply *rs )
 	}
 
 	scopes = scope_chunk_get( op );
-	stack = search_stack( op );
+	candidates = c0 = search_stack( op );
+	iscopes = candidates + MDB_idl_um_size;
+	stack = iscopes + MDB_idl_db_size;
+	/* if candidates already in use, alloc a new array */
+	if ( c0[0] ) {
+		candidates = ch_malloc(( MDB_idl_um_size + MDB_idl_db_size ) * sizeof ( ID ));
+		iscopes = candidates + MDB_idl_um_size;
+	}
 	isc.mt = ltid;
 	isc.mc = mcd;
 	isc.scopes = scopes;
@@ -1215,6 +1221,11 @@ done:
 	if (base)
 		mdb_entry_return( op, base );
 	scope_chunk_ret( op, scopes );
+	if ( candidates != c0 ) {
+		ch_free( candidates );
+	} else {
+		MDB_IDL_ZERO( candidates );
+	}
 
 	return rs->sr_err;
 }
@@ -1268,6 +1279,11 @@ static int oc_filter(
 	return rc;
 }
 
+typedef struct IDLchunk {
+	unsigned int logn;
+	unsigned int pad;
+} IDLchunk;
+
 static void search_stack_free( void *key, void *data )
 {
 	ber_memfree_x(data, NULL);
@@ -1276,26 +1292,34 @@ static void search_stack_free( void *key, void *data )
 static void *search_stack( Operation *op )
 {
 	struct mdb_info *mdb = (struct mdb_info *) op->o_bd->be_private;
-	void *ret = NULL;
+	IDLchunk *ic = NULL;
 
 	if ( op->o_threadctx ) {
 		ldap_pvt_thread_pool_getkey( op->o_threadctx, (void *)search_stack,
-			&ret, NULL );
+			(void **)&ic, NULL );
 	} else {
-		ret = mdb->mi_search_stack;
+		ic = mdb->mi_search_stack;
 	}
 
-	if ( !ret ) {
-		ret = ch_malloc( mdb->mi_search_stack_depth * MDB_idl_um_size
-			* sizeof( ID ) );
+	if ( ic && ic->logn != MDB_idl_logn ) {
+		ber_memfree_x( ic, NULL );
+		ic = NULL;
+	}
+
+	if ( !ic ) {
+		ic = ch_malloc(( mdb->mi_search_stack_depth + 2 ) * MDB_idl_um_size
+			* sizeof( ID ) + sizeof( IDLchunk ) );
+		ic->logn = MDB_idl_logn;
 		if ( op->o_threadctx ) {
 			ldap_pvt_thread_pool_setkey( op->o_threadctx, (void *)search_stack,
-				ret, search_stack_free, NULL, NULL );
+				ic, search_stack_free, NULL, NULL );
 		} else {
-			mdb->mi_search_stack = ret;
+			mdb->mi_search_stack = ic;
 		}
+		ID *idl = (ID *)( ic+1 );
+		MDB_IDL_ZERO( idl );
 	}
-	return ret;
+	return ic+1;
 }
 
 static int search_candidates(