PCI: designware: Require config accesses to be naturally aligned

Add sanity checks on "addr" input parameter in dw_pcie_cfg_read() and
dw_pcie_cfg_write().  These checks make sure that accesses are aligned on
their size, e.g., a 4-byte config access is aligned on a 4-byte boundary.

[bhelgaas: changelog, set *val = 0 in failure case]
Signed-off-by: Gabriele Paoloni <gabriele.paoloni@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Pratyush Anand <pratyush.anand@gmail.com>

drivers/pci/host/pcie-designware.c

@@ -82,6 +82,11 @@ static inline struct pcie_port *sys_to_pcie(struct pci_sys_data *sys)
 
 int dw_pcie_cfg_read(void __iomem *addr, int size, u32 *val)
 {
+	if ((uintptr_t)addr & (size - 1)) {
+		*val = 0;
+		return PCIBIOS_BAD_REGISTER_NUMBER;
+	}
+
 	if (size == 4)
 		*val = readl(addr);
 	else if (size == 2)
@@ -98,6 +103,9 @@ int dw_pcie_cfg_read(void __iomem *addr, int size, u32 *val)
 
 int dw_pcie_cfg_write(void __iomem *addr, int size, u32 val)
 {
+	if ((uintptr_t)addr & (size - 1))
+		return PCIBIOS_BAD_REGISTER_NUMBER;
+
 	if (size == 4)
 		writel(val, addr);
 	else if (size == 2)