Subject: Re: [PATCH 1/1] Defer skb allocation for both mergeable buffers and big packets in virtio_net

From: Shirley Ma <[email-masked]>
Date: Fri, 20 Nov 2009 08:08:52 -0800

On Fri, 2009-11-20 at 07:19 +0100, Eric Dumazet wrote:
> > +void virtio_free_pages(void *buf)
> > +{
> > +     struct page *page = (struct page *)buf;
> > +
> > +     while (page) {
> > +             __free_pages(page, 0);
> > +             page = (struct page *)page->private;
> > +     }
> > +}
> > +
> 
> Interesting use after free :)

Good catch. This code was run when virtio_net removal. I run many times
of remove virtio_net, and didn't hit any panic :(. Fixed it as below:

void virtio_free_pages(void *buf)
{
	struct page *page = (struct page *)buf;
	struct page *npage;

	while (page) {
		npage = page->private;
		__free_pages(page, 0);
		page = npage;
	}
}

Thanks
Shirley