Re: [Qemu-devel] [PATCH 03/12] VMDK: probe for mono flat image

[Stefan Hajnoczi]

On Wed, Jun 15, 2011 at 5:26 AM, Fam Zheng <address@hidden> wrote:
> On Tue, Jun 14, 2011 at 4:06 PM, Stefan Hajnoczi <address@hidden> wrote:
>> On Sat, Jun 04, 2011 at 08:40:50AM +0800, Fam Zheng wrote:
>>> vmdk_probe for mono flat images.
>>>
>>> Signed-off-by: Fam Zheng <address@hidden>
>>> ---
>>>  block/vmdk.c |   13 ++++++++++---
>>>  1 files changed, 10 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/block/vmdk.c b/block/vmdk.c
>>> index f787528..bf8d02a 100644
>>> --- a/block/vmdk.c
>>> +++ b/block/vmdk.c
>>> @@ -101,10 +101,17 @@ static int vmdk_probe(const uint8_t *buf, int
>>> buf_size, const char *filename)
>>>          return 0;
>>>      magic = be32_to_cpu(*(uint32_t *)buf);
>>>      if (magic == VMDK3_MAGIC ||
>>> -        magic == VMDK4_MAGIC)
>>> +        magic == VMDK4_MAGIC) {
>>>          return 100;
>>> -    else
>>> -        return 0;
>>> +    } else {
>>> +        char *cid_p, *ct_p, *extent_p;
>>> +        cid_p = strstr((char *)buf, "CID");
>>> +        ct_p = strstr((char *)buf, "createType");
>>> +        extent_p = strstr((char *)buf, "RW");
>>> +        if (cid_p && ct_p && extent_p)
>>> +            return 100;
>>
>> NUL-terminated string functions cannot be used for probing because the
>> input file may be invalid.  If the magic number matches but there is no
>> NUL in the buffer then the strstr(3) will run off the end of the buffer.
>>
>> Also note that the specification says "The descriptor file is not
>> case-sensitive".  "cid", "CiD", and "CID" should all be allowed.
>>
>> Do non-monolithic vmdk images always have "# Disk DescriptorFile" as the
>> first line?  Perhaps you can test for that using memcmp(3) instead.
> No guarantee in specification, although VMware does start descriptors
> with such a line "# Disk DescriptorFile".
> But is it proper that we make this assumption?

Have you tried removing that comment line to see if VMware still
recognizes the file?

Stefan