Re: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg_node

Michael S. Tsirkin
2018-04-27T16:15:32Z

On Fri, Apr 27, 2018 at 06:11:31PM +0200, Dmitry Vyukov wrote:
> On Fri, Apr 27, 2018 at 6:05 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Fri, Apr 27, 2018 at 11:45:02AM -0400, Kevin Easton wrote:
> >> The struct vhost_msg within struct vhost_msg_node is copied to userspace,
> >> so it should be allocated with kzalloc() to ensure all structure padding
> >> is zeroed.
> >>
> >> Signed-off-by: Kevin Easton <kevin@guarana.org>
> >> Reported-by: syzbot+87cfa083e727a224754b@syzkaller.appspotmail.com
> >
> > Does it help if a patch naming the padding is applied,
> > and then we init just the relevant field?
> > Just curious.
>
> Yes, it would help.

I think it's slightly better that way then. node has a lot of internal
stuff we don't care to init. Would you mind taking my patch and building
on top of that then?

> >> ---
> >> drivers/vhost/vhost.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> >> index f3bd8e9..1b84dcff 100644
> >> --- a/drivers/vhost/vhost.c
> >> +++ b/drivers/vhost/vhost.c
> >> @@ -2339,7 +2339,7 @@ EXPORT_SYMBOL_GPL(vhost_disable_notify);
> >> /* Create a new message. */
> >> struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type)
> >> {
> >> - struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL);
> >> + struct vhost_msg_node *node = kzalloc(sizeof *node, GFP_KERNEL);
> >> if (!node)
> >> return NULL;
> >> node->vq = vq;
> >> --
> >> 2.8.1
> >
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