Re: [Qemu-block] [Qemu-devel] [PATCH] xen-disk: use g_malloc0 to fix build

[Daniel P. Berrange]

On Fri, Jul 28, 2017 at 07:43:59AM -0500, Eric Blake wrote:
> On 07/28/2017 07:31 AM, Olaf Hering wrote:
> > g_malloc0_n is available since glib-2.24. To allow build with older glib
> > versions use the generic g_malloc0, which is already used in many other
> > places in the code.
> > 
> > Fixes commit 3284fad728 ("xen-disk: add support for multi-page shared 
> > rings")
> > 
> > Signed-off-by: Olaf Hering <address@hidden>
> > ---
> >  hw/block/xen_disk.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> > index d42ed7070d..71deec17b0 100644
> > --- a/hw/block/xen_disk.c
> > +++ b/hw/block/xen_disk.c
> > @@ -1232,7 +1232,7 @@ static int blk_connect(struct XenDevice *xendev)
> >          return -1;
> >      }
> >  
> > -    domids = g_malloc0_n(blkdev->nr_ring_ref, sizeof(uint32_t));
> > +    domids = g_malloc0(blkdev->nr_ring_ref * sizeof(uint32_t));
> 
> This version is prone to multiplication overflow (well, maybe not, but
> you have to audit for that).  Wouldn't it be better to use:
> 
> domids = g_new0(blkdev->nr_ring_ref, uint32_t)

You mean   g_new0(uint32_t, blkdev->nr_ring_ref)  but yeah, g_new0 is
better than g_malloc0 pretty much every time.

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|