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

Kevin Easton
2018-05-08T08:27:20Z

On Mon, May 07, 2018 at 04:03:25PM +0300, Michael S. Tsirkin 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
> > ---
> > 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;
>
>
> Let's just init the msg though.
>
> OK it seems this is the best we can do for now,
> we need a new feature bit to fix it for 32 bit
> userspace on 64 bit kernels.
>
> Does the following help?

Yes, the reproducer doesn't trigger the error with that patch applied.

- Kevin