[PATCH v2 4/6] PCI/VPD: Reject resource tags with invalid size

[Bjorn Helgaas <helgaas@kernel.org>]

From: Bjorn Helgaas <bhelgaas@google.com>

VPD is limited in size by the 15-bit VPD Address field in the VPD
Capability.  Each resource tag includes a length that determines the
overall size of the resource.  Reject any resources that would extend past
the maximum VPD size.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/pci/vpd.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/vpd.c b/drivers/pci/vpd.c
index 66703de2cf2b..e52382050e3e 100644
--- a/drivers/pci/vpd.c
+++ b/drivers/pci/vpd.c
@@ -77,6 +77,7 @@ static size_t pci_vpd_size(struct pci_dev *dev, size_t old_size)
 
 	while (off < old_size && pci_read_vpd(dev, off, 1, header) == 1) {
 		unsigned char tag;
+		size_t size;
 
 		if (off == 0 && (header[0] == 0x00 || header[0] == 0xff))
 			goto error;
@@ -94,8 +95,11 @@ static size_t pci_vpd_size(struct pci_dev *dev, size_t old_size)
 						 off + 1);
 					return 0;
 				}
-				off += PCI_VPD_LRDT_TAG_SIZE +
-					pci_vpd_lrdt_size(header);
+				size = pci_vpd_lrdt_size(header);
+				if (off + size > PCI_VPD_MAX_SIZE)
+					goto error;
+
+				off += PCI_VPD_LRDT_TAG_SIZE + size;
 			} else {
 				pci_warn(dev, "invalid large VPD tag %02x at offset %zu",
 					 tag, off);
@@ -103,9 +107,12 @@ static size_t pci_vpd_size(struct pci_dev *dev, size_t old_size)
 			}
 		} else {
 			/* Short Resource Data Type Tag */
-			off += PCI_VPD_SRDT_TAG_SIZE +
-				pci_vpd_srdt_size(header);
 			tag = pci_vpd_srdt_tag(header);
+			size = pci_vpd_srdt_size(header);
+			if (size == 0 || off + size > PCI_VPD_MAX_SIZE)
+				goto error;
+
+			off += PCI_VPD_SRDT_TAG_SIZE + size;
 			if (tag == PCI_VPD_STIN_END)	/* End tag descriptor */
 				return off;
 		}
-- 
2.25.1