PCI: Bounds-check command-line resource alignment requests

32-bit BARs are limited to 2GB size (2^31).  By extension, I assume 64-bit
BARs are limited to 2^63 bytes.  Limit the alignment requested by the
"pci=resource_alignment=" command-line parameter to 2^63.

Link: https://lore.kernel.org/r/20201007123045.GS4282@kadam
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.c

@@ -6202,19 +6202,21 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
 	while (*p) {
 		count = 0;
 		if (sscanf(p, "%d%n", &align_order, &count) == 1 &&
-							p[count] == '@') {
+		    p[count] == '@') {
 			p += count + 1;
+			if (align_order > 63) {
+				pr_err("PCI: Invalid requested alignment (order %d)\n",
+				       align_order);
+				align_order = PAGE_SHIFT;
+			}
 		} else {
-			align_order = -1;
+			align_order = PAGE_SHIFT;
 		}
 
 		ret = pci_dev_str_match(dev, p, &p);
 		if (ret == 1) {
 			*resize = true;
-			if (align_order == -1)
-				align = PAGE_SIZE;
-			else
-				align = 1 << align_order;
+			align = 1 << align_order;
 			break;
 		} else if (ret < 0) {
 			pr_err("PCI: Can't parse resource_alignment parameter: %s\n",