> On Wed, 19 Aug 2020 15:13:49 +0200
> Lorenzo Bianconi <lorenzo@xxxxxxxxxx> wrote:
>
> > diff --git a/net/core/xdp.c b/net/core/xdp.c
> > index 884f140fc3be..006b24b5d276 100644
> > --- a/net/core/xdp.c
> > +++ b/net/core/xdp.c
> > @@ -370,19 +370,55 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct)
> >
> > void xdp_return_frame(struct xdp_frame *xdpf)
> > {
> > + struct skb_shared_info *sinfo;
> > + int i;
> > +
> > __xdp_return(xdpf->data, &xdpf->mem, false);
>
> There is a use-after-free race here. The xdpf->data contains the
> shared_info (xdp_get_shared_info_from_frame(xdpf)). Thus you cannot
> free/return the page and use this data area below.
right, thx for pointing this out. I will fix it in v2.
Regards,
Lorenzo
>
> > + if (!xdpf->mb)
> > + return;
> > +
> > + sinfo = xdp_get_shared_info_from_frame(xdpf);
> > + for (i = 0; i < sinfo->nr_frags; i++) {
> > + struct page *page = skb_frag_page(&sinfo->frags[i]);
> > +
> > + __xdp_return(page_address(page), &xdpf->mem, false);
> > + }
> > }
> > EXPORT_SYMBOL_GPL(xdp_return_frame);
> >
> > void xdp_return_frame_rx_napi(struct xdp_frame *xdpf)
> > {
> > + struct skb_shared_info *sinfo;
> > + int i;
> > +
> > __xdp_return(xdpf->data, &xdpf->mem, true);
>
> Same issue.
>
> > + if (!xdpf->mb)
> > + return;
> > +
> > + sinfo = xdp_get_shared_info_from_frame(xdpf);
> > + for (i = 0; i < sinfo->nr_frags; i++) {
> > + struct page *page = skb_frag_page(&sinfo->frags[i]);
> > +
> > + __xdp_return(page_address(page), &xdpf->mem, true);
> > + }
> > }
> > EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);
> >
> > void xdp_return_buff(struct xdp_buff *xdp)
> > {
> > + struct skb_shared_info *sinfo;
> > + int i;
> > +
> > __xdp_return(xdp->data, &xdp->rxq->mem, true);
>
> Same issue.
>
> > + if (!xdp->mb)
> > + return;
> > +
> > + sinfo = xdp_get_shared_info_from_buff(xdp);
> > + for (i = 0; i < sinfo->nr_frags; i++) {
> > + struct page *page = skb_frag_page(&sinfo->frags[i]);
> > +
> > + __xdp_return(page_address(page), &xdp->rxq->mem, true);
> > + }
> > }
>
>
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
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