Re: [PATCH v2] net: ipv6: fix use-after-free Read in __xfrm6_tunnel_spi_lookup

[Steffen Klassert]

On Sat, Jul 25, 2020 at 10:35:12PM -0700, Cong Wang wrote:
> On Sat, Jul 25, 2020 at 8:09 PM B K Karthik <bkkarthik@xxxxxxxxxxxx> wrote:
> > @@ -103,10 +103,10 @@ static int __xfrm6_tunnel_spi_check(struct net *net, u32 spi)
> >  {
> >         struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);
> >         struct xfrm6_tunnel_spi *x6spi;
> > -       int index = xfrm6_tunnel_spi_hash_byspi(spi);
> > +       int index = xfrm6_tunnel_spi_hash_byaddr((const xfrm_address_t *)spi);
> >
> >         hlist_for_each_entry(x6spi,
> > -                            &xfrm6_tn->spi_byspi[index],
> > +                            &xfrm6_tn->spi_byaddr[index],
> >                              list_byspi) {
> >                 if (x6spi->spi == spi)
> 
> How did you convince yourself this is correct? This lookup is still
> using spi. :)

This can not be correct, it takes a u32 spi value and casts it to a
pointer to an IP address.