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

[Fam Zheng <famcool@gmail.com>]

On Tue, Jun 14, 2011 at 4:06 PM, Stefan Hajnoczi <stefanha@gmail.com> 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 <famcool@gmail.com>
>> ---
>>  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?


-- 
Best regards!
Fam Zheng