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Date: Wed, 15 Jun 2011 06:31:14 +0100
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From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH 03/12] VMDK: probe for mono flat image
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To: Fam Zheng <famcool@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org, Christoph Hellwig <hch@lst.de>

On Wed, Jun 15, 2011 at 5:26 AM, Fam Zheng <famcool@gmail.com> wrote:
> On Tue, Jun 14, 2011 at 4:06 PM, Stefan Hajnoczi <stefanha@gmail.com> wro=
te:
>> 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>
>>> ---
>>> =A0block/vmdk.c | =A0 13 ++++++++++---
>>> =A01 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)
>>> =A0 =A0 =A0 =A0 =A0return 0;
>>> =A0 =A0 =A0magic =3D be32_to_cpu(*(uint32_t *)buf);
>>> =A0 =A0 =A0if (magic =3D=3D VMDK3_MAGIC ||
>>> - =A0 =A0 =A0 =A0magic =3D=3D VMDK4_MAGIC)
>>> + =A0 =A0 =A0 =A0magic =3D=3D VMDK4_MAGIC) {
>>> =A0 =A0 =A0 =A0 =A0return 100;
>>> - =A0 =A0else
>>> - =A0 =A0 =A0 =A0return 0;
>>> + =A0 =A0} else {
>>> + =A0 =A0 =A0 =A0char *cid_p, *ct_p, *extent_p;
>>> + =A0 =A0 =A0 =A0cid_p =3D strstr((char *)buf, "CID");
>>> + =A0 =A0 =A0 =A0ct_p =3D strstr((char *)buf, "createType");
>>> + =A0 =A0 =A0 =A0extent_p =3D strstr((char *)buf, "RW");
>>> + =A0 =A0 =A0 =A0if (cid_p && ct_p && extent_p)
>>> + =A0 =A0 =A0 =A0 =A0 =A0return 100;
>>
>> NUL-terminated string functions cannot be used for probing because the
>> input file may be invalid. =A0If the magic number matches but there is n=
o
>> 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". =A0"cid", "CiD", and "CID" should all be allowed.
>>
>> Do non-monolithic vmdk images always have "# Disk DescriptorFile" as the
>> first line? =A0Perhaps 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