s3:registry: fix race in reg_setvalue that could lead to data corruption

(there was no lock around fetching the values and storing them)

The layering is wrong in that it uses regdb transactions in reg_api
(cherry picked from commit 9220377ceebf05e756fd108cbd30b503598e0fb8)

diff --git a/source3/registry/reg_api.c b/source3/registry/reg_api.c
index bdf5ae13e096b5efa586f6a248249da700456109..bd3cabb86e5f803013e9bda76c38aab3e3bd29b8 100644 (file)
--- a/source3/registry/reg_api.c
+++ b/source3/registry/reg_api.c
@@ -711,10 +711,17 @@ WERROR reg_setvalue(struct registry_key *key, const char *name,
                return WERR_ACCESS_DENIED;
        }
 
+       err = regdb_transaction_start();
+       if (!W_ERROR_IS_OK(err)) {
+               DEBUG(0, ("reg_setvalue: Failed to start transaction: %s\n",
+                         win_errstr(err)));
+               return err;
+       }
+
        err = fill_value_cache(key);
        if (!W_ERROR_IS_OK(err)) {
                DEBUG(0, ("reg_setvalue: Error filling value cache: %s\n", win_errstr(err)));
-               return err;
+               goto done;
        }
 
        existing = regval_ctr_getvalue(key->values, name);
@@ -722,8 +729,10 @@ WERROR reg_setvalue(struct registry_key *key, const char *name,
        if ((existing != NULL) &&
            (regval_size(existing) == val->data.length) &&
            (memcmp(regval_data_p(existing), val->data.data,
-                   val->data.length) == 0)) {
-               return WERR_OK;
+                   val->data.length) == 0))
+       {
+               err = WERR_OK;
+               goto done;
        }
 
        res = regval_ctr_addvalue(key->values, name, val->type,
@@ -731,15 +740,33 @@ WERROR reg_setvalue(struct registry_key *key, const char *name,
 
        if (res == 0) {
                TALLOC_FREE(key->values);
-               return WERR_NOMEM;
+               err = WERR_NOMEM;
+               goto done;
        }
 
        if (!store_reg_values(key->key, key->values)) {
                TALLOC_FREE(key->values);
-               return WERR_REG_IO_FAILURE;
+               DEBUG(0, ("reg_setvalue: store_reg_values failed\n"));
+               err = WERR_REG_IO_FAILURE;
+               goto done;
        }
 
-       return WERR_OK;
+       err = WERR_OK;
+
+done:
+       if (W_ERROR_IS_OK(err)) {
+               err = regdb_transaction_commit();
+               if (!W_ERROR_IS_OK(err)) {
+                       DEBUG(0, ("reg_setvalue: Error committing transaction: %s\n", win_errstr(err)));
+               }
+       } else {
+               WERROR err1 = regdb_transaction_cancel();
+               if (!W_ERROR_IS_OK(err1)) {
+                       DEBUG(0, ("reg_setvalue: Error cancelling transaction: %s\n", win_errstr(err1)));
+               }
+       }
+
+       return err;
 }
 
 static WERROR reg_value_exists(struct registry_key *key, const char *name)