linux-hardening - Re: [PATCH] hte: Annotate struct hte_device with __counted

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Date: Thu, 28 Sep 2023 13:42:39 +0900
From: Justin Stitt <justinstitt@...gle.com>
To: Kees Cook <keescook@...omium.org>
Cc: Dipen Patel <dipenp@...dia.com>, timestamp@...ts.linux.dev, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Tom Rix <trix@...hat.com>, 
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] hte: Annotate struct hte_device with __counted_by

On Sat, Sep 23, 2023 at 2:54 AM 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 checking 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 hte_device.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Dipen Patel <dipenp@...dia.com>
> Cc: timestamp@...ts.linux.dev
> Signed-off-by: Kees Cook <keescook@...omium.org>

Yep, this flexible array member is counted by @nlines which
is evident throughout hte.c:

        gdev = kzalloc(struct_size(gdev, ei, chip->nlines), GFP_KERNEL);
        ...
        gdev->nlines = chip->nlines;
        ...
        for (i = 0; i < chip->nlines; i++) {
          gdev->ei[i].gdev = gdev;
        ...


Reviewed-by: Justin Stitt <justinstitt@...gle.com>

> ---
>  drivers/hte/hte.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hte/hte.c b/drivers/hte/hte.c
> index 598a716b7364..1fd8d2d4528b 100644
> --- a/drivers/hte/hte.c
> +++ b/drivers/hte/hte.c
> @@ -88,7 +88,7 @@ struct hte_device {
>         struct list_head list;
>         struct hte_chip *chip;
>         struct module *owner;
> -       struct hte_ts_info ei[];
> +       struct hte_ts_info ei[] __counted_by(nlines);
>  };
>
>  #ifdef CONFIG_DEBUG_FS
> --
> 2.34.1
>
>