[PATCH v2 06/18] virtio: pci: Check virtio capability is in bounds

[Andrew Scull]

Ensure the virtio PCI capabilities are contained within the bounds of
the device's configuration space. The expected size of the capability is
passed when searching for the capability to enforce this check.

Signed-off-by: Andrew Scull <ascull at google.com>
---
 drivers/virtio/virtio_pci_modern.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 2c1b0ebfce..6fe5e76572 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -397,18 +397,27 @@ static int virtio_pci_notify(struct udevice *udev, struct virtqueue *vq)
  *
  * @udev:	the transport device
  * @cfg_type:	the VIRTIO_PCI_CAP_* value we seek
+ * @cap_size:	expected size of the capability
  *
  * Return: offset of the configuration structure
  */
-static int virtio_pci_find_capability(struct udevice *udev, u8 cfg_type)
+static int virtio_pci_find_capability(struct udevice *udev, u8 cfg_type,
+				      size_t cap_size)
 {
 	int pos;
 	int offset;
 	u8 type, bar;
 
+	assert(cap_size >= sizeof(struct virtio_pci_cap));
+	assert(cap_size <= PCI_CFG_SPACE_SIZE);
+
 	for (pos = dm_pci_find_capability(udev, PCI_CAP_ID_VNDR);
 	     pos > 0;
 	     pos = dm_pci_find_next_capability(udev, pos, PCI_CAP_ID_VNDR)) {
+		/* Ensure the capability is within bounds */
+		if (PCI_CFG_SPACE_SIZE - cap_size < pos)
+			return 0;
+
 		offset = pos + offsetof(struct virtio_pci_cap, cfg_type);
 		dm_pci_read_config8(udev, offset, &type);
 		offset = pos + offsetof(struct virtio_pci_cap, bar);
@@ -496,7 +505,8 @@ static int virtio_pci_probe(struct udevice *udev)
 	uc_priv->vendor = subvendor;
 
 	/* Check for a common config: if not, use legacy mode (bar 0) */
-	common = virtio_pci_find_capability(udev, VIRTIO_PCI_CAP_COMMON_CFG);
+	common = virtio_pci_find_capability(udev, VIRTIO_PCI_CAP_COMMON_CFG,
+					    sizeof(struct virtio_pci_cap));
 	if (!common) {
 		printf("(%s): leaving for legacy driver\n", udev->name);
 		return -ENODEV;
@@ -510,7 +520,8 @@ static int virtio_pci_probe(struct udevice *udev)
 	}
 
 	/* If common is there, notify should be too */
-	notify = virtio_pci_find_capability(udev, VIRTIO_PCI_CAP_NOTIFY_CFG);
+	notify = virtio_pci_find_capability(udev, VIRTIO_PCI_CAP_NOTIFY_CFG,
+					    sizeof(struct virtio_pci_notify_cap));
 	if (!notify) {
 		printf("(%s): missing capabilities %i/%i\n", udev->name,
 		       common, notify);
@@ -524,7 +535,8 @@ static int virtio_pci_probe(struct udevice *udev)
 	 * Device capability is only mandatory for devices that have
 	 * device-specific configuration.
 	 */
-	device = virtio_pci_find_capability(udev, VIRTIO_PCI_CAP_DEVICE_CFG);
+	device = virtio_pci_find_capability(udev, VIRTIO_PCI_CAP_DEVICE_CFG,
+					    sizeof(struct virtio_pci_cap));
 	if (device) {
 		offset = device + offsetof(struct virtio_pci_cap, length);
 		dm_pci_read_config32(udev, offset, &priv->device_len);
-- 
2.35.1.1021.g381101b075-goog