diff mbox

[2/2] pci: Update VPD size with correct length

Message ID 1450427719-29619-3-git-send-email-hare@suse.de (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show

Commit Message

Hannes Reinecke Dec. 18, 2015, 8:35 a.m. UTC 
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.
Trying to read VPD data beyond that marker results in 'interesting'
effects, from simple read errors to crashing the card. And to make
matters worse not every PCI card implements this properly, leaving
us with no 'end' marker or even completely invalid data.
This path modifies the size of the VPD attribute to the available
size, or set it to '0' if no valid data could be read.

Cc: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/pci/access.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.h    |  1 +
 2 files changed, 82 insertions(+)

Comments

Alexander Duyck Dec. 18, 2015, 1:49 p.m. UTC | #1 
On Fri, Dec 18, 2015 at 12:35 AM, Hannes Reinecke <hare@suse.de> wrote:
> 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.
> Trying to read VPD data beyond that marker results in 'interesting'
> effects, from simple read errors to crashing the card. And to make
> matters worse not every PCI card implements this properly, leaving
> us with no 'end' marker or even completely invalid data.
> This path modifies the size of the VPD attribute to the available
> size, or set it to '0' if no valid data could be read.

This isn't what I had in mind.  There is no need to add an f0 version
of the size function.  The size for all functions other than function
0 when the F0 flag is set is 0.  We aren't going to be reading their
VPD, we only read the VPD region of function 0.

If you just  moved the call to pci_vpd_size into the conditional
statement in the init function you could then set the length to 0 in
the branch taken for if the F0 flag is set.  You might have to reorder
the init function a bit but there is no need to add additional
function pointers.

- Alex
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Hannes Reinecke Dec. 18, 2015, 1:57 p.m. UTC | #2 
On 12/18/2015 02:49 PM, Alexander Duyck wrote:
> On Fri, Dec 18, 2015 at 12:35 AM, Hannes Reinecke <hare@suse.de> wrote:
>> 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.
>> Trying to read VPD data beyond that marker results in 'interesting'
>> effects, from simple read errors to crashing the card. And to make
>> matters worse not every PCI card implements this properly, leaving
>> us with no 'end' marker or even completely invalid data.
>> This path modifies the size of the VPD attribute to the available
>> size, or set it to '0' if no valid data could be read.
>
> This isn't what I had in mind.  There is no need to add an f0 version
> of the size function.  The size for all functions other than function
> 0 when the F0 flag is set is 0.  We aren't going to be reading their
> VPD, we only read the VPD region of function 0.
>
Ah. (I'm a bit confused about the proposed action for VPD other than 
function 0).
So the idea here is to _disallow_ access to VPDs from functions 
other than '0' unless these functions have different PCI IDs?

Cheers,

Hannes
Alexander Duyck Dec. 18, 2015, 2:02 p.m. UTC | #3 
On Fri, Dec 18, 2015 at 5:57 AM, Hannes Reinecke <hare@suse.de> wrote:
> On 12/18/2015 02:49 PM, Alexander Duyck wrote:
>>
>> On Fri, Dec 18, 2015 at 12:35 AM, Hannes Reinecke <hare@suse.de> wrote:
>>>
>>> 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.
>>> Trying to read VPD data beyond that marker results in 'interesting'
>>> effects, from simple read errors to crashing the card. And to make
>>> matters worse not every PCI card implements this properly, leaving
>>> us with no 'end' marker or even completely invalid data.
>>> This path modifies the size of the VPD attribute to the available
>>> size, or set it to '0' if no valid data could be read.
>>
>>
>> This isn't what I had in mind.  There is no need to add an f0 version
>> of the size function.  The size for all functions other than function
>> 0 when the F0 flag is set is 0.  We aren't going to be reading their
>> VPD, we only read the VPD region of function 0.
>>
> Ah. (I'm a bit confused about the proposed action for VPD other than
> function 0).
> So the idea here is to _disallow_ access to VPDs from functions other than
> '0' unless these functions have different PCI IDs?

If you take a look at the F0 functions what they do is bypass the VPD
of the functions other than function 0.  As such setting the size to 0
should really have no effect since the VPD of the function isn't
actually read if the F0 flag is set.

- Alex
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Hannes Reinecke Dec. 18, 2015, 2:14 p.m. UTC | #4 
On 12/18/2015 03:02 PM, Alexander Duyck wrote:
> On Fri, Dec 18, 2015 at 5:57 AM, Hannes Reinecke <hare@suse.de> wrote:
>> On 12/18/2015 02:49 PM, Alexander Duyck wrote:
>>>
>>> On Fri, Dec 18, 2015 at 12:35 AM, Hannes Reinecke <hare@suse.de> wrote:
>>>>
>>>> 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.
>>>> Trying to read VPD data beyond that marker results in 'interesting'
>>>> effects, from simple read errors to crashing the card. And to make
>>>> matters worse not every PCI card implements this properly, leaving
>>>> us with no 'end' marker or even completely invalid data.
>>>> This path modifies the size of the VPD attribute to the available
>>>> size, or set it to '0' if no valid data could be read.
>>>
>>>
>>> This isn't what I had in mind.  There is no need to add an f0 version
>>> of the size function.  The size for all functions other than function
>>> 0 when the F0 flag is set is 0.  We aren't going to be reading their
>>> VPD, we only read the VPD region of function 0.
>>>
>> Ah. (I'm a bit confused about the proposed action for VPD other than
>> function 0).
>> So the idea here is to _disallow_ access to VPDs from functions other than
>> '0' unless these functions have different PCI IDs?
>
> If you take a look at the F0 functions what they do is bypass the VPD
> of the functions other than function 0.  As such setting the size to 0
> should really have no effect since the VPD of the function isn't
> actually read if the F0 flag is set.
>
Setting the size to '0' effectively inhibits you to read the VPD 
data. So if we were to return '0' for PCI devices with the F0 bit 
set we will never ever to be able to read (or write) _any_ VPD data 
for that PCI device/function.
Which would be rendering all these F0 accessors pointless, and we 
might as well remove them.

Hence my confusion.

Cheers,

Hannes
diff mbox

Patch

diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 59ac36f..2e23fc7 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -206,6 +206,18 @@  ssize_t pci_write_vpd(struct pci_dev *dev, loff_t pos, size_t count, const void
 }
 EXPORT_SYMBOL(pci_write_vpd);
 
+/**
+ * pci_vpd_size - Determine the size of the Vital Product Data
+ * @dev:	pci device struct
+ *
+ */
+size_t pci_vpd_size(struct pci_dev *dev)
+{
+	if (!dev->vpd || !dev->vpd->ops)
+		return 0;
+	return dev->vpd->ops->size(dev);
+}
+
 /*
  * The following routines are to prevent the user from accessing PCI config
  * space when it's unsafe to do so.  Some devices require this during BIST and
@@ -428,6 +440,53 @@  out:
 	return ret ? ret : count;
 }
 
+/**
+ * pci_vpd_size - determine actual size of Vital Product Data
+ * @dev:	pci device struct
+ *
+ */
+static size_t pci_vpd_pci22_size(struct pci_dev *dev)
+{
+	ssize_t off = 0;
+	unsigned char header[1+2];	/* 1 byte tag, 2 bytes length */
+
+	while (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)
+					return off + 1;
+				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_dbg(&dev->dev,
+				"invalid %s vpd tag %02x at offset %zu.",
+				(header[0] & PCI_VPD_LRDT) ? "large" : "short",
+				tag, off);
+			break;
+		}
+	}
+	return 0;
+}
+
 static void pci_vpd_pci22_release(struct pci_dev *dev)
 {
 	kfree(container_of(dev->vpd, struct pci_vpd_pci22, base));
@@ -436,6 +495,7 @@  static void pci_vpd_pci22_release(struct pci_dev *dev)
 static const struct pci_vpd_ops pci_vpd_pci22_ops = {
 	.read = pci_vpd_pci22_read,
 	.write = pci_vpd_pci22_write,
+	.size = pci_vpd_pci22_size,
 	.release = pci_vpd_pci22_release,
 };
 
@@ -469,9 +529,29 @@  static ssize_t pci_vpd_f0_write(struct pci_dev *dev, loff_t pos, size_t count,
 	return ret;
 }
 
+static size_t pci_vpd_f0_size(struct pci_dev *dev)
+{
+	struct pci_dev *tdev = pci_get_slot(dev->bus,
+					    PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
+	ssize_t len = 0;
+
+	if (!tdev)
+		return 0;
+
+	if (tdev->vpd) {
+		struct pci_vpd_pci22 *vpd =
+			container_of(dev->vpd, struct pci_vpd_pci22, base);
+
+		len = vpd->base.len;
+	}
+	pci_dev_put(tdev);
+	return len;
+}
+
 static const struct pci_vpd_ops pci_vpd_f0_ops = {
 	.read = pci_vpd_f0_read,
 	.write = pci_vpd_f0_write,
+	.size = pci_vpd_f0_size,
 	.release = pci_vpd_pci22_release,
 };
 
@@ -497,6 +577,7 @@  int pci_vpd_pci22_init(struct pci_dev *dev)
 	vpd->cap = cap;
 	vpd->busy = false;
 	dev->vpd = &vpd->base;
+	vpd->base.len = pci_vpd_size(dev);
 	return 0;
 }
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index fd2f03f..33dfc7c 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -97,6 +97,7 @@  static inline bool pci_has_subordinate(struct pci_dev *pci_dev)
 struct pci_vpd_ops {
 	ssize_t (*read)(struct pci_dev *dev, loff_t pos, size_t count, void *buf);
 	ssize_t (*write)(struct pci_dev *dev, loff_t pos, size_t count, const void *buf);
+	size_t (*size)(struct pci_dev *dev);
 	void (*release)(struct pci_dev *dev);
 };