pci: Update VPD size with correct length
diff mbox

Message ID 1445591396-95395-1-git-send-email-hare@suse.de
State Changes Requested
Headers show

Commit Message

Hannes Reinecke Oct. 23, 2015, 9:09 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.
This path modifies the attribute size to the avialable VPD size.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/pci/access.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

Comments

kernel test robot Oct. 23, 2015, 10:47 a.m. UTC | #1
Hi Hannes,

[auto build test WARNING on pci/next -- if it's inappropriate base, please suggest rules for selecting the more suitable base]

url:    https://github.com/0day-ci/linux/commits/Hannes-Reinecke/pci-Update-VPD-size-with-correct-length/20151023-171224
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

>> drivers/pci/access.c:499:1: sparse: symbol 'pci_vpd_pci22_size' was not declared. Should it be static?

Please review and possibly fold the followup patch.

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Alexander Duyck Oct. 24, 2015, 12:52 a.m. UTC | #2
On 10/23/2015 02:09 AM, Hannes Reinecke 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.
> This path modifies the attribute size to the avialable VPD size.
>
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
>   drivers/pci/access.c | 29 +++++++++++++++++++++++++++++
>   1 file changed, 29 insertions(+)
>
> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> index 6bc9b12..4f8208e 100644
> --- a/drivers/pci/access.c
> +++ b/drivers/pci/access.c
> @@ -409,6 +409,34 @@ static int pci_vpd_f0_dev_check(struct pci_dev *dev)
>   	return ret;
>   }
>
> +/**
> + * pci_vpd_size - determine actual size of Vital Product Data
> + * @dev:	pci device struct
> + * @old_size:	current assumed size, also maximum allowed size
> + *
> + */
> +size_t
> +pci_vpd_pci22_size(struct pci_dev *dev, size_t old_size)
> +{
> +	loff_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)) {
> +		if (header[0] == 0x78)	/* End tag descriptor */
> +			return off + 1;
> +		if (header[0] & 0x80) {
> +			/* Large Resource Data Type Tag */
> +			if (pci_read_vpd(dev, off+1, 2, &header[1]) != 2)
> +				return off + 1;
> +			off += 3 + ((header[2] << 8) | header[1]);
> +		} else {
> +			/* Short Resource Data Type Tag */
> +			off += 1 + (header[0] & 0x07);
> +		}
> +	}
> +	return old_size;
> +}
> +

My understanding is that the end tag can have some data associated with 
it such as a checksum.  What you may want to look at doing is process 
long tag and short tag bits first.  Then you could do a mask and compare 
after and if ((header[0] & ~0x7) == 0x78) then you return off + 1.

Also I was wondering if you have looked at the cxgb4 network driver? 
They are using the vpd read/write calls to access their EEPROM and I 
assume they are doing so outside the actual VPD fields.

- Alex
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Hannes Reinecke Oct. 25, 2015, 3:34 a.m. UTC | #3
On 10/24/2015 02:52 AM, Alexander Duyck wrote:
> On 10/23/2015 02:09 AM, Hannes Reinecke 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.
>> This path modifies the attribute size to the avialable VPD size.
>>
>> Signed-off-by: Hannes Reinecke <hare@suse.de>
>> ---
>>   drivers/pci/access.c | 29 +++++++++++++++++++++++++++++
>>   1 file changed, 29 insertions(+)
>>
>> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
>> index 6bc9b12..4f8208e 100644
>> --- a/drivers/pci/access.c
>> +++ b/drivers/pci/access.c
>> @@ -409,6 +409,34 @@ static int pci_vpd_f0_dev_check(struct pci_dev *dev)
>>       return ret;
>>   }
>>
>> +/**
>> + * pci_vpd_size - determine actual size of Vital Product Data
>> + * @dev:    pci device struct
>> + * @old_size:    current assumed size, also maximum allowed size
>> + *
>> + */
>> +size_t
>> +pci_vpd_pci22_size(struct pci_dev *dev, size_t old_size)
>> +{
>> +    loff_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)) {
>> +        if (header[0] == 0x78)    /* End tag descriptor */
>> +            return off + 1;
>> +        if (header[0] & 0x80) {
>> +            /* Large Resource Data Type Tag */
>> +            if (pci_read_vpd(dev, off+1, 2, &header[1]) != 2)
>> +                return off + 1;
>> +            off += 3 + ((header[2] << 8) | header[1]);
>> +        } else {
>> +            /* Short Resource Data Type Tag */
>> +            off += 1 + (header[0] & 0x07);
>> +        }
>> +    }
>> +    return old_size;
>> +}
>> +
> 
> My understanding is that the end tag can have some data associated with
> it such as a checksum.  What you may want to look at doing is process
> long tag and short tag bits first.  Then you could do a mask and compare
> after and if ((header[0] & ~0x7) == 0x78) then you return off + 1.
> 
Ah. Oh. Hmm. Wasn't aware of that one.
Bjorn?

> Also I was wondering if you have looked at the cxgb4 network driver?
> They are using the vpd read/write calls to access their EEPROM and I
> assume they are doing so outside the actual VPD fields.
> 
As indicated; VPD page access is basically directly wired to the device.
So if the vendor chooses to do some extra magic there by all means let
him do so. This patch is meant for cards/vendors which (try) to adhere
to the PCI VPD specification, so our access to that should be
conformant, too.

Cheers,

Hannes
Bjorn Helgaas Nov. 25, 2015, 5:17 p.m. UTC | #4
Hi Hannes,

On Sun, Oct 25, 2015 at 04:34:34AM +0100, Hannes Reinecke wrote:
> On 10/24/2015 02:52 AM, Alexander Duyck wrote:
> > On 10/23/2015 02:09 AM, Hannes Reinecke 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.
> >> This path modifies the attribute size to the avialable VPD size.
> >>
> >> Signed-off-by: Hannes Reinecke <hare@suse.de>
> >> ---
> >>   drivers/pci/access.c | 29 +++++++++++++++++++++++++++++
> >>   1 file changed, 29 insertions(+)
> >>
> >> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> >> index 6bc9b12..4f8208e 100644
> >> --- a/drivers/pci/access.c
> >> +++ b/drivers/pci/access.c
> >> @@ -409,6 +409,34 @@ static int pci_vpd_f0_dev_check(struct pci_dev *dev)
> >>       return ret;
> >>   }
> >>
> >> +/**
> >> + * pci_vpd_size - determine actual size of Vital Product Data
> >> + * @dev:    pci device struct
> >> + * @old_size:    current assumed size, also maximum allowed size
> >> + *
> >> + */
> >> +size_t
> >> +pci_vpd_pci22_size(struct pci_dev *dev, size_t old_size)
> >> +{
> >> +    loff_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)) {
> >> +        if (header[0] == 0x78)    /* End tag descriptor */
> >> +            return off + 1;
> >> +        if (header[0] & 0x80) {
> >> +            /* Large Resource Data Type Tag */
> >> +            if (pci_read_vpd(dev, off+1, 2, &header[1]) != 2)
> >> +                return off + 1;
> >> +            off += 3 + ((header[2] << 8) | header[1]);
> >> +        } else {
> >> +            /* Short Resource Data Type Tag */
> >> +            off += 1 + (header[0] & 0x07);
> >> +        }
> >> +    }
> >> +    return old_size;
> >> +}
> >> +
> > 
> > My understanding is that the end tag can have some data associated with
> > it such as a checksum.  What you may want to look at doing is process
> > long tag and short tag bits first.  Then you could do a mask and compare
> > after and if ((header[0] & ~0x7) == 0x78) then you return off + 1.
> > 
> Ah. Oh. Hmm. Wasn't aware of that one.
> Bjorn?

I don't know.  I took a very quick glance at the PCI 3.0 spec and I
didn't see the description of data associated with an End Tag.  It'd
be nice to have a spec reference for whatever we implement here.

It sounds like this fixes some real problems, and it'd also be nice to
have more specifics about them, e.g., what devices, how to reproduce,
etc.

Bjorn
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Alexander Duyck Nov. 25, 2015, 6:01 p.m. UTC | #5
On 11/25/2015 09:17 AM, Bjorn Helgaas wrote:
> Hi Hannes,
>
> On Sun, Oct 25, 2015 at 04:34:34AM +0100, Hannes Reinecke wrote:
>> On 10/24/2015 02:52 AM, Alexander Duyck wrote:
>>> On 10/23/2015 02:09 AM, Hannes Reinecke 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.
>>>> This path modifies the attribute size to the avialable VPD size.
>>>>
>>>> Signed-off-by: Hannes Reinecke <hare@suse.de>
>>>> ---
>>>>    drivers/pci/access.c | 29 +++++++++++++++++++++++++++++
>>>>    1 file changed, 29 insertions(+)
>>>>
>>>> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
>>>> index 6bc9b12..4f8208e 100644
>>>> --- a/drivers/pci/access.c
>>>> +++ b/drivers/pci/access.c
>>>> @@ -409,6 +409,34 @@ static int pci_vpd_f0_dev_check(struct pci_dev *dev)
>>>>        return ret;
>>>>    }
>>>>
>>>> +/**
>>>> + * pci_vpd_size - determine actual size of Vital Product Data
>>>> + * @dev:    pci device struct
>>>> + * @old_size:    current assumed size, also maximum allowed size
>>>> + *
>>>> + */
>>>> +size_t
>>>> +pci_vpd_pci22_size(struct pci_dev *dev, size_t old_size)
>>>> +{
>>>> +    loff_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)) {
>>>> +        if (header[0] == 0x78)    /* End tag descriptor */
>>>> +            return off + 1;
>>>> +        if (header[0] & 0x80) {
>>>> +            /* Large Resource Data Type Tag */
>>>> +            if (pci_read_vpd(dev, off+1, 2, &header[1]) != 2)
>>>> +                return off + 1;
>>>> +            off += 3 + ((header[2] << 8) | header[1]);
>>>> +        } else {
>>>> +            /* Short Resource Data Type Tag */
>>>> +            off += 1 + (header[0] & 0x07);
>>>> +        }
>>>> +    }
>>>> +    return old_size;
>>>> +}
>>>> +
>>>
>>> My understanding is that the end tag can have some data associated with
>>> it such as a checksum.  What you may want to look at doing is process
>>> long tag and short tag bits first.  Then you could do a mask and compare
>>> after and if ((header[0] & ~0x7) == 0x78) then you return off + 1.
>>>
>> Ah. Oh. Hmm. Wasn't aware of that one.
>> Bjorn?
>
> I don't know.  I took a very quick glance at the PCI 3.0 spec and I
> didn't see the description of data associated with an End Tag.  It'd
> be nice to have a spec reference for whatever we implement here.

I had originally based my suggestion to include length off an example I 
saw in the third edition of "PCI System Architecture".  However it 
didn't explain things very well so I did some digging.

The end tag was defined in the Plug and Play ISA Specification, Version 
1.0a, section 6.2.2.11.  There the end tag  supported 1 byte of data for 
a checksum.  I believe the PCI 3.0 spec calls this out as the reference 
for the small tags and as such we probably should support it.

It is highly likely that there may be implementations that followed the 
above example and have end tags that may have an additional byte 
dangling off of them for the checksum.  So I would say it is worth it to 
cover at least that case.

- Alex
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Patch
diff mbox

diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 6bc9b12..4f8208e 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -409,6 +409,34 @@  static int pci_vpd_f0_dev_check(struct pci_dev *dev)
 	return ret;
 }
 
+/**
+ * pci_vpd_size - determine actual size of Vital Product Data
+ * @dev:	pci device struct
+ * @old_size:	current assumed size, also maximum allowed size
+ *
+ */
+size_t
+pci_vpd_pci22_size(struct pci_dev *dev, size_t old_size)
+{
+	loff_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)) {
+		if (header[0] == 0x78)	/* End tag descriptor */
+			return off + 1;
+		if (header[0] & 0x80) {
+			/* Large Resource Data Type Tag */
+			if (pci_read_vpd(dev, off+1, 2, &header[1]) != 2)
+				return off + 1;
+			off += 3 + ((header[2] << 8) | header[1]);
+		} else {
+			/* Short Resource Data Type Tag */
+			off += 1 + (header[0] & 0x07);
+		}
+	}
+	return old_size;
+}
+
 int pci_vpd_pci22_init(struct pci_dev *dev)
 {
 	struct pci_vpd_pci22 *vpd;
@@ -436,6 +464,7 @@  int pci_vpd_pci22_init(struct pci_dev *dev)
 	vpd->cap = cap;
 	vpd->busy = false;
 	dev->vpd = &vpd->base;
+	vpd->base.len = pci_vpd_pci22_size(dev, vpd->base.len);
 	return 0;
 }