ucmd: module: dm: don't write garbage keys

If SID fails to get the sysfs dm sysfs values, likely because the
device has been removed from sysfs, fail instead of using uninitialized
memory for the key.

src/modules/ucmd/type/dm/dm.c

@@ -170,12 +170,18 @@ static int _dm_ident(struct module *module, struct sid_ucmd_ctx *ucmd_ctx)
 	log_debug(DM_ID, "ident");
 
 	snprintf(path, sizeof(path), "%s%s/dm/uuid", SYSTEM_SYSFS_PATH, sid_ucmd_event_get_dev_path(ucmd_ctx));
-	sid_util_sysfs_get_value(path, uuid, sizeof(uuid));
+	if (sid_util_sysfs_get_value(path, uuid, sizeof(uuid)) < 0) {
+		log_error(DM_ID, "Failed to get DM uuid.");
+		return -1;
+	}
 	sid_ucmd_dev_add_alias(module, ucmd_ctx, "uuid", uuid);
 	sid_ucmd_set_kv(module, ucmd_ctx, KV_NS_DEVMOD, "uuid", uuid, strlen(uuid) + 1, KV_SYNC | KV_SUB_RD);
 
 	snprintf(path, sizeof(path), "%s%s/dm/name", SYSTEM_SYSFS_PATH, sid_ucmd_event_get_dev_path(ucmd_ctx));
-	sid_util_sysfs_get_value(path, name, sizeof(name));
+	if (sid_util_sysfs_get_value(path, name, sizeof(name)) < 0) {
+		log_error(DM_ID, "Failed to get DM name.");
+		return -1;
+	}
 	sid_ucmd_dev_add_alias(module, ucmd_ctx, "name", name);
 	sid_ucmd_set_kv(module, ucmd_ctx, KV_NS_DEVMOD, "name", name, strlen(name) + 1, KV_SYNC | KV_SUB_RD);