PCI: xilinx: Check for __get_free_pages() failure

If __get_free_pages() fails, return -ENOMEM to avoid a NULL pointer
dereference.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

drivers/pci/controller/pcie-xilinx.c

@@ -336,14 +336,19 @@ static const struct irq_domain_ops msi_domain_ops = {
  * xilinx_pcie_enable_msi - Enable MSI support
  * @port: PCIe port information
  */
-static void xilinx_pcie_enable_msi(struct xilinx_pcie_port *port)
+static int xilinx_pcie_enable_msi(struct xilinx_pcie_port *port)
 {
 	phys_addr_t msg_addr;
 
 	port->msi_pages = __get_free_pages(GFP_KERNEL, 0);
+	if (!port->msi_pages)
+		return -ENOMEM;
+
 	msg_addr = virt_to_phys((void *)port->msi_pages);
 	pcie_write(port, 0x0, XILINX_PCIE_REG_MSIBASE1);
 	pcie_write(port, msg_addr, XILINX_PCIE_REG_MSIBASE2);
+
+	return 0;
 }
 
 /* INTx Functions */
@@ -498,6 +503,7 @@ static int xilinx_pcie_init_irq_domain(struct xilinx_pcie_port *port)
 	struct device *dev = port->dev;
 	struct device_node *node = dev->of_node;
 	struct device_node *pcie_intc_node;
+	int ret;
 
 	/* Setup INTx */
 	pcie_intc_node = of_get_next_child(node, NULL);
@@ -526,7 +532,9 @@ static int xilinx_pcie_init_irq_domain(struct xilinx_pcie_port *port)
 			return -ENODEV;
 		}
 
-		xilinx_pcie_enable_msi(port);
+		ret = xilinx_pcie_enable_msi(port);
+		if (ret)
+			return ret;
 	}
 
 	return 0;