iwlwifi: fix kernel oops when ucode DMA memory allocation failure

The patch fixes memcpy to NULL address when the ucode DMA allocation failure.

This is a fix to bug
http://www.intellinuxwireless.org/bugzilla/show_bug.cgi?id=1861

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -1719,6 +1719,10 @@ static int iwl_read_ucode(struct iwl_priv *priv)
 	priv->ucode_data_backup.len = data_size;
 	iwl_alloc_fw_desc(priv->pci_dev, &priv->ucode_data_backup);
 
+	if (!priv->ucode_code.v_addr || !priv->ucode_data.v_addr ||
+	    !priv->ucode_data_backup.v_addr)
+		goto err_pci_alloc;
+
 	/* Initialization instructions and data */
 	if (init_size && init_data_size) {
 		priv->ucode_init.len = init_size;