Re: [Qemu-devel] [PATCH for-2.8 v1 1/1] block/vmdk: Fix the endian problem of buf_len

[Hao QingFeng]

在 2016-11-25 18:21, Kevin Wolf 写道:
> [ Cc: Fam, qemu-stable ]
>
> Am 25.11.2016 um 11:06 hat QingFeng Hao geschrieben:
> > The problem was triggered by qemu-iotests case 055. It failed when it
> > was comparing the compressed vmdk image with original test.img.
> >
> > The cause is that buf_len in vmdk_write_extent wasn't converted to
> > little-endian before it was stored to disk. But later vmdk_read_extent
> > read it and converted it from little-endian to cpu endian.
> > If the cpu is big-endian like s390, the problem will happen and
> > the data length read by vmdk_read_extent will become invalid!
> > The fix is to add the conversion in vmdk_write_extent.
> >
> > Signed-off-by: QingFeng Hao <address@hidden>
> > Signed-off-by: Jing Liu <address@hidden>
> Sounds like something that should still be fixed for 2.8 and in the
> stable branches.
I didn't find the stable branch on upstream, the latest is 2.6 maybe 
it's a private one? :-)
> > diff --git a/block/vmdk.c b/block/vmdk.c
> > index a11c27a..bf6667f 100644
> > --- a/block/vmdk.c
> > +++ b/block/vmdk.c
> > @@ -1355,7 +1355,7 @@ static int vmdk_write_extent(VmdkExtent *extent, int64_t 
> > cluster_offset,
> >           }
> >   
> >           data->lba = offset >> BDRV_SECTOR_BITS;
> > -        data->size = buf_len;
> > +        data->size = cpu_to_le32(buf_len);
> At least data->lba needs to be fixed, too, both here and in
> vmdk_read_extent(). Host endianness in an image file is always wrong.
Good detection!
> Maybe we should audit the whole driver for endianness problems.
Good sight! maybe we can encapsulate a suite of endianness functions
for the structures to avoid missing some elements of them like lba?
Also will be better for reuse. When I am checking the endianness calls
in vmdk_create_extent, I am just afraid of missing one. :-)
Thanks!
> Kevin

--
QingFeng Hao(Robin)