s4-ldb: validate the type of the ldb argument to ldb_dn_new()

It has been a common bug to get the first two arguments the wrong way
around

diff --git a/source4/lib/ldb/common/ldb_dn.c b/source4/lib/ldb/common/ldb_dn.c
index 79953c6018451bcd7d0243f52d473fd1764820c3..252a0c632b16178277b5ab3e14c4d603f5c9b69a 100644 (file)
--- a/source4/lib/ldb/common/ldb_dn.c
+++ b/source4/lib/ldb/common/ldb_dn.c
@@ -103,7 +103,13 @@ struct ldb_dn *ldb_dn_from_ldb_val(void *mem_ctx,
        dn = talloc_zero(mem_ctx, struct ldb_dn);
        LDB_DN_NULL_FAILED(dn);
 
        dn = talloc_zero(mem_ctx, struct ldb_dn);
        LDB_DN_NULL_FAILED(dn);
 

-       dn->ldb = ldb;
+       dn->ldb = talloc_get_type(ldb, struct ldb_context);
+       if (dn->ldb == NULL) {
+               /* the caller probably got the arguments to
+                  ldb_dn_new() mixed up */
+               talloc_free(dn);
+               return NULL;
+       }

 
        if (strdn->data && strdn->length) {
                const char *data = (const char *)strdn->data;
 
        if (strdn->data && strdn->length) {
                const char *data = (const char *)strdn->data;