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

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 [off-list ref] wrote:

quoted

@@ -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.