[PATCH v6 2/2] net/virtio: fix PCI config err handling

[Luca Boccassi <bluca@debian.org>]

From: Brian Russell <brussell@brocade.com>

In virtio_read_caps and vtpci_msix_detect, rte_pci_read_config returns
the number of bytes read from PCI config or < 0 on error.
If less than the expected number of bytes are read then log the
failure and return rather than carrying on with garbage.

Fixes: 6ba1f63b5ab0 ("virtio: support specification 1.0")

Signed-off-by: Brian Russell <brussell@brocade.com>
Signed-off-by: Luca Boccassi <bluca@debian.org>
---
v2: handle additional rte_pci_read_config incomplete reads
v3: do not handle rte_pci_read_config of virtio cap, added in v2,
    as it's less clear what the right thing to do there is
v4: do a more robust check - first check what the vendor is, and
    skip the cap entirely if it's not what we are looking for.
v5: fetch only 2 flags bytes if the vndr is PCI_CAP_ID_MSIX
v6: fix 32bit build by changing the printf format specifier, fix patch title

 drivers/net/virtio/virtio_pci.c | 65 ++++++++++++++++++++++++---------
 1 file changed, 48 insertions(+), 17 deletions(-)

diff --git a/drivers/net/virtio/virtio_pci.c b/drivers/net/virtio/virtio_pci.c
index 6bd22e54a6..b6a3c80b4d 100644
--- a/drivers/net/virtio/virtio_pci.c
+++ b/drivers/net/virtio/virtio_pci.c
@@ -567,16 +567,18 @@ virtio_read_caps(struct rte_pci_device *dev, struct virtio_hw *hw)
 	}
 
 	ret = rte_pci_read_config(dev, &pos, 1, PCI_CAPABILITY_LIST);
-	if (ret < 0) {
-		PMD_INIT_LOG(DEBUG, "failed to read pci capability list");
+	if (ret != 1) {
+		PMD_INIT_LOG(DEBUG,
+			     "failed to read pci capability list, ret %d", ret);
 		return -1;
 	}
 
 	while (pos) {
-		ret = rte_pci_read_config(dev, &cap, sizeof(cap), pos);
-		if (ret < 0) {
-			PMD_INIT_LOG(ERR,
-				"failed to read pci cap at pos: %x", pos);
+		ret = rte_pci_read_config(dev, &cap, 2, pos);
+		if (ret != 2) {
+			PMD_INIT_LOG(DEBUG,
+				     "failed to read pci cap at pos: %x ret %d",
+				     pos, ret);
 			break;
 		}
 
@@ -586,7 +588,16 @@ virtio_read_caps(struct rte_pci_device *dev, struct virtio_hw *hw)
 			 * 1st byte is cap ID; 2nd byte is the position of next
 			 * cap; next two bytes are the flags.
 			 */
-			uint16_t flags = ((uint16_t *)&cap)[1];
+			uint16_t flags;
+
+			ret = rte_pci_read_config(dev, &flags, sizeof(flags),
+					pos + 2);
+			if (ret != sizeof(flags)) {
+				PMD_INIT_LOG(DEBUG,
+					     "failed to read pci cap at pos:"
+					     " %x ret %d", pos + 2, ret);
+				break;
+			}
 
 			if (flags & PCI_MSIX_ENABLE)
 				hw->use_msix = VIRTIO_MSIX_ENABLED;
@@ -601,6 +612,14 @@ virtio_read_caps(struct rte_pci_device *dev, struct virtio_hw *hw)
 			goto next;
 		}
 
+		ret = rte_pci_read_config(dev, &cap, sizeof(cap), pos);
+		if (ret != sizeof(cap)) {
+			PMD_INIT_LOG(DEBUG,
+				     "failed to read pci cap at pos: %x ret %d",
+				     pos, ret);
+			break;
+		}
+
 		PMD_INIT_LOG(DEBUG,
 			"[%2x] cfg type: %u, bar: %u, offset: %04x, len: %u",
 			pos, cap.cfg_type, cap.bar, cap.offset, cap.length);
@@ -689,25 +708,37 @@ enum virtio_msix_status
 vtpci_msix_detect(struct rte_pci_device *dev)
 {
 	uint8_t pos;
-	struct virtio_pci_cap cap;
 	int ret;
 
 	ret = rte_pci_read_config(dev, &pos, 1, PCI_CAPABILITY_LIST);
-	if (ret < 0) {
-		PMD_INIT_LOG(DEBUG, "failed to read pci capability list");
+	if (ret != 1) {
+		PMD_INIT_LOG(DEBUG,
+			     "failed to read pci capability list, ret %d", ret);
 		return VIRTIO_MSIX_NONE;
 	}
 
 	while (pos) {
-		ret = rte_pci_read_config(dev, &cap, sizeof(cap), pos);
-		if (ret < 0) {
-			PMD_INIT_LOG(ERR,
-				"failed to read pci cap at pos: %x", pos);
+		uint8_t cap[2];
+
+		ret = rte_pci_read_config(dev, cap, sizeof(cap), pos);
+		if (ret != sizeof(cap)) {
+			PMD_INIT_LOG(DEBUG,
+				     "failed to read pci cap at pos: %x ret %d",
+				     pos, ret);
 			break;
 		}
 
-		if (cap.cap_vndr == PCI_CAP_ID_MSIX) {
-			uint16_t flags = ((uint16_t *)&cap)[1];
+		if (cap[0] == PCI_CAP_ID_MSIX) {
+			uint16_t flags;
+
+			ret = rte_pci_read_config(dev, &flags, sizeof(flags),
+					pos + sizeof(cap));
+			if (ret != sizeof(flags)) {
+				PMD_INIT_LOG(DEBUG,
+					     "failed to read pci cap at pos:"
+					     " %x ret %d", pos + 2, ret);
+				break;
+			}
 
 			if (flags & PCI_MSIX_ENABLE)
 				return VIRTIO_MSIX_ENABLED;
@@ -715,7 +746,7 @@ vtpci_msix_detect(struct rte_pci_device *dev)
 				return VIRTIO_MSIX_DISABLED;
 		}
 
-		pos = cap.cap_next;
+		pos = cap[1];
 	}
 
 	return VIRTIO_MSIX_NONE;
-- 
2.18.0