Re: [Qemu-devel] [PATCH] vmdk: byteswap VMDK4Header.desc_offset field

[Stefan Hajnoczi <stefanha@gmail.com>]

On Mon, Jun 10, 2013 at 04:04:55PM +0200, Kevin Wolf wrote:
> Am 10.06.2013 um 11:07 hat Stefan Hajnoczi geschrieben:
> > Remember to byteswap VMDK4Header.desc_offset on big-endian machines.
> > 
> > Cc: qemu-stable@nongnu.org
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> 
> Thanks, applied to the block layer.
> 
> > @@ -507,8 +507,11 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
> >      if (ret < 0) {
> >          return ret;
> >      }
> > -    if (header.capacity == 0 && header.desc_offset) {
> > -        return vmdk_open_desc_file(bs, flags, header.desc_offset << 9);
> > +    if (header.capacity == 0) {
> > +        int64_t desc_offset = le64_to_cpu(header.desc_offset);
> > +        if (desc_offset) {
> > +            return vmdk_open_desc_file(bs, flags, desc_offset << 9);
> > +        }
> >      }
> 
> Splitting up the if condition wouldn't have been necessary, strictly
> speaking. But I don't mind too much here.

True.  The reason I did it is because accessing header.desc_offset
directly is a bad habit.  Someone modifying the code might conclude it's
safe to access directly when it actually only works for the limited
cases of zero and non-zero.

Stefan