Re: [PATCH 54/64] ipv6: Use struct_group() to zero rt6_info

Jakub Kicinski
2021-07-29T18:58:58Z

On Tue, 27 Jul 2021 13:58:45 -0700 Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memset(), avoid intentionally writing across
> neighboring fields.
>
> Add struct_group() to mark region of struct rt6_info that should be
> initialized to zero.

memset_after() ?

> diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
> index 15b7fbe6b15c..9816e7444918 100644
> --- a/include/net/ip6_fib.h
> +++ b/include/net/ip6_fib.h
> @@ -205,20 +205,22 @@ struct fib6_info {
>
> struct rt6_info {
> struct dst_entry dst;
> - struct fib6_info __rcu *from;
> - int sernum;
> -
> - struct rt6key rt6i_dst;
> - struct rt6key rt6i_src;
> - struct in6_addr rt6i_gateway;
> - struct inet6_dev *rt6i_idev;
> - u32 rt6i_flags;
> -
> - struct list_head rt6i_uncached;
> - struct uncached_list *rt6i_uncached_list;
> -
> - /* more non-fragment space at head required */
> - unsigned short rt6i_nfheader_len;
> + struct_group(init,
> + struct fib6_info __rcu *from;
> + int sernum;
> +
> + struct rt6key rt6i_dst;
> + struct rt6key rt6i_src;
> + struct in6_addr rt6i_gateway;
> + struct inet6_dev *rt6i_idev;
> + u32 rt6i_flags;
> +
> + struct list_head rt6i_uncached;
> + struct uncached_list *rt6i_uncached_list;
> +
> + /* more non-fragment space at head required */
> + unsigned short rt6i_nfheader_len;
> + );
> };
>
> struct fib6_result {
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 6b8051106aba..bbcc605bab57 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -327,9 +327,7 @@ static const struct rt6_info ip6_blk_hole_entry_template = {
>
> static void rt6_info_init(struct rt6_info *rt)
> {
> - struct dst_entry *dst = &rt->dst;
> -
> - memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
> + memset(&rt->init, 0, sizeof(rt->init));
> INIT_LIST_HEAD(&rt->rt6i_uncached);
> }
>