linux-hardening - Re: [PATCH] net/mlx5: Annotate struct mlx5_fc_bulk with __counted

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Message-ID: <CAFhGd8p_o5xtmrV+Vm0JUR5VQmMenqtm3xbJuE0TSj-_4Bthfw@mail.gmail.com>
Date: Tue, 3 Oct 2023 16:21:05 -0700
From: Justin Stitt <justinstitt@...gle.com>
To: Kees Cook <keescook@...omium.org>
Cc: Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	linux-rdma@...r.kernel.org, "Gustavo A. R. Silva" <gustavoars@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Tom Rix <trix@...hat.com>, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
	llvm@...ts.linux.dev
Subject: Re: [PATCH] net/mlx5: Annotate struct mlx5_fc_bulk with __counted_by

On Tue, Oct 3, 2023 at 4:17 PM Kees Cook <keescook@...omium.org> 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 mlx5_fc_bulk.
>
> Cc: Saeed Mahameed <saeedm@...dia.com>
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: netdev@...r.kernel.org
> Cc: linux-rdma@...r.kernel.org
> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
> index 17fe30a4c06c..0c26d707eed2 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
> @@ -539,7 +539,7 @@ struct mlx5_fc_bulk {
>         u32 base_id;
>         int bulk_len;
>         unsigned long *bitmask;
> -       struct mlx5_fc fcs[];
> +       struct mlx5_fc fcs[] __counted_by(bulk_len);
>  };

This looks good.

`bulk->bulk_len` is assigned before flexible array member `fcs` is accessed.

        bulk->bulk_len = bulk_len;
        for (i = 0; i < bulk_len; i++) {
                mlx5_fc_init(&bulk->fcs[i], bulk, base_id + i);
                set_bit(i, bulk->bitmask);
        }

Reviewed-by: Justin Stitt <justinstitt@...gle.com>
>
>  static void mlx5_fc_init(struct mlx5_fc *counter, struct mlx5_fc_bulk *bulk,
> --
> 2.34.1
>
>
Thanks
Justin