Re: [PATCH] net/packet: Annotate struct packet_fanout with __counted_by

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

On 10/4/23 01:17, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct packet_fanout.
> 
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Anqi Shen <amy.saq@antgroup.com>
> Cc: netdev@vger.kernel.org
> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
--
Gustavo

> ---
>   net/packet/internal.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/packet/internal.h b/net/packet/internal.h
> index 63f4865202c1..d29c94c45159 100644
> --- a/net/packet/internal.h
> +++ b/net/packet/internal.h
> @@ -94,7 +94,7 @@ struct packet_fanout {
>   	spinlock_t		lock;
>   	refcount_t		sk_ref;
>   	struct packet_type	prot_hook ____cacheline_aligned_in_smp;
> -	struct sock	__rcu	*arr[];
> +	struct sock	__rcu	*arr[] __counted_by(max_num_members);
>   };
>   
>   struct packet_rollover {