Re: [PATCH linux-2.6.18-xen] blkback: don't call vbd_size() if bd_disk is NULL

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, May 25, 2011 at 11:36:04AM +0100, Jan Beulich wrote:
> >>> On 25.05.11 at 12:24, Laszlo Ersek <lersek@redhat.com> wrote:
> > ...because vbd_size() dereferences bd_disk if bd_part is NULL.

Which would imply that doing this on disk without any partitions would crash.

Weird, I don't seem to get that problem on a disk without any
partitions (just a raw disk). Or does the kernel actually set the
bd_part to something even if it does not have any partitions?

> > 
> > Signed-off-by: Laszlo Ersek<lersek@redhat.com>
> 
> Acked-by: Jan Beulich <jbeulich@novell.com>
> 
> > ---
> >   drivers/xen/blkback/vbd.c |    3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff -r 415a9b435fef drivers/xen/blkback/vbd.c
> > --- a/drivers/xen/blkback/vbd.c	Mon May 23 18:36:33 2011 +0100
> > +++ b/drivers/xen/blkback/vbd.c	Wed May 25 12:15:26 2011 +0200
> > @@ -73,7 +73,6 @@ int vbd_create(blkif_t *blkif, blkif_vde
> >   	}
> > 
> >   	vbd->bdev = bdev;
> > -	vbd->size = vbd_size(vbd);
> > 
> >   	if (vbd->bdev->bd_disk == NULL) {
> >   		DPRINTK("vbd_creat: device %08x doesn't exist.\n",
> > @@ -82,6 +81,8 @@ int vbd_create(blkif_t *blkif, blkif_vde
> >   		return -ENOENT;
> >   	}
> > 
> > +	vbd->size = vbd_size(vbd);
> > +
> >   	if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
> >   		vbd->type |= VDISK_CDROM;
> >   	if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
> > 
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> > Xen-devel@lists.xensource.com 
> > http://lists.xensource.com/xen-devel 
> 
> 
> 
> 
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