PCI: Determine actual VPD size on first access

hreinecke · bjorn-helgaas · commit 104daa71b396 · 2016-02-29T17:47:04.000-06:00
PCI-2.2 VPD entries have a maximum size of 32k, but might actually be
smaller than that.  To figure out the actual size one has to read the VPD
area until the 'end marker' is reached.

Per spec, reading outside of the VPD space is "not allowed."  In practice,
it may cause simple read errors or even crash the card.  To make matters
worse not every PCI card implements this properly, leaving us with no 'end'
marker or even completely invalid data.

Try to determine the size of the VPD data when it's first accessed.  If no
valid data can be read an I/O error will be returned when reading or
writing the sysfs attribute.

As the amount of VPD data is unknown initially the size of the sysfs
attribute will always be set to '0'.

[bhelgaas: changelog, use 0/1 (not false/true) for bitfield, tweak
pci_vpd_pci22_read() error checking]
Tested-by: Shane Seymour &lt;shane.seymour@hpe.com&gt;
Tested-by: Babu Moger &lt;babu.moger@oracle.com&gt;
Signed-off-by: Hannes Reinecke &lt;hare@suse.de&gt;
Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Cc: Alexander Duyck &lt;alexander.duyck@gmail.com&gt;
diff --git a/drivers/pci/access.c b/drivers/pci/access.c
@@ -285,8 +285,63 @@ struct pci_vpd_pci22 {
 	u16	flag;
 	u8	cap;
 	u8	busy:1;
+	u8	valid:1;
 };
 
+/**
+ * pci_vpd_size - determine actual size of Vital Product Data
+ * @dev:	pci device struct
+ * @old_size:	current assumed size, also maximum allowed size
+ */
+static size_t pci_vpd_pci22_size(struct pci_dev *dev, size_t old_size)
+{
+	size_t off = 0;
+	unsigned char header[1+2];	/* 1 byte tag, 2 bytes length */
+
+	while (off < old_size &&
+	       pci_read_vpd(dev, off, 1, header) == 1) {
+		unsigned char tag;
+
+		if (header[0] & PCI_VPD_LRDT) {
+			/* Large Resource Data Type Tag */
+			tag = pci_vpd_lrdt_tag(header);
+			/* Only read length from known tag items */
+			if ((tag == PCI_VPD_LTIN_ID_STRING) ||
+			    (tag == PCI_VPD_LTIN_RO_DATA) ||
+			    (tag == PCI_VPD_LTIN_RW_DATA)) {
+				if (pci_read_vpd(dev, off+1, 2,
+						 &header[1]) != 2) {
+					dev_warn(&dev->dev,
+						 "invalid large VPD tag %02x size at offset %zu",
+						 tag, off + 1);
+					return 0;
+				}
+				off += PCI_VPD_LRDT_TAG_SIZE +
+					pci_vpd_lrdt_size(header);
+			}
+		} else {
+			/* Short Resource Data Type Tag */
+			off += PCI_VPD_SRDT_TAG_SIZE +
+				pci_vpd_srdt_size(header);
+			tag = pci_vpd_srdt_tag(header);
+		}
+
+		if (tag == PCI_VPD_STIN_END)	/* End tag descriptor */
+			return off;
+
+		if ((tag != PCI_VPD_LTIN_ID_STRING) &&
+		    (tag != PCI_VPD_LTIN_RO_DATA) &&
+		    (tag != PCI_VPD_LTIN_RW_DATA)) {
+			dev_warn(&dev->dev,
+				 "invalid %s VPD tag %02x at offset %zu",
+				 (header[0] & PCI_VPD_LRDT) ? "large" : "short",
+				 tag, off);
+			return 0;
+		}
+	}
+	return 0;
+}
+
 /*
  * Wait for last operation to complete.
  * This code has to spin since there is no other notification from the PCI
@@ -337,9 +392,25 @@ static ssize_t pci_vpd_pci22_read(struct pci_dev *dev, loff_t pos, size_t count,
 	loff_t end = pos + count;
 	u8 *buf = arg;
 
-	if (pos < 0 || pos > vpd->base.len || end > vpd->base.len)
+	if (pos < 0)
 		return -EINVAL;
 
+	if (!vpd->valid) {
+		vpd->valid = 1;
+		vpd->base.len = pci_vpd_pci22_size(dev, vpd->base.len);
+	}
+
+	if (vpd->base.len == 0)
+		return -EIO;
+
+	if (pos >= vpd->base.len)
+		return 0;
+
+	if (end > vpd->base.len) {
+		end = vpd->base.len;
+		count = end - pos;
+	}
+
 	if (mutex_lock_killable(&vpd->lock))
 		return -EINTR;
 
@@ -389,7 +460,18 @@ static ssize_t pci_vpd_pci22_write(struct pci_dev *dev, loff_t pos, size_t count
 	loff_t end = pos + count;
 	int ret = 0;
 
-	if (pos < 0 || (pos & 3) || (count & 3) || end > vpd->base.len)
+	if (pos < 0 || (pos & 3) || (count & 3))
+		return -EINVAL;
+
+	if (!vpd->valid) {
+		vpd->valid = 1;
+		vpd->base.len = pci_vpd_pci22_size(dev, vpd->base.len);
+	}
+
+	if (vpd->base.len == 0)
+		return -EIO;
+
+	if (end > vpd->base.len)
 		return -EINVAL;
 
 	if (mutex_lock_killable(&vpd->lock))
@@ -496,6 +578,7 @@ int pci_vpd_pci22_init(struct pci_dev *dev)
 	mutex_init(&vpd->lock);
 	vpd->cap = cap;
 	vpd->busy = 0;
+	vpd->valid = 0;
 	dev->vpd = &vpd->base;
 	return 0;
 }
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
@@ -1323,7 +1323,7 @@ static int pci_create_capabilities_sysfs(struct pci_dev *dev)
 			return -ENOMEM;
 
 		sysfs_bin_attr_init(attr);
-		attr->size = dev->vpd->len;
+		attr->size = 0;
 		attr->attr.name = "vpd";
 		attr->attr.mode = S_IRUSR | S_IWUSR;
 		attr->read = read_vpd_attr;
