linux-kernel - Re: [PATCH] dm crypt: Annotate struct crypt_config with __counted

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Message-ID: <030807ff-5fc0-3461-565e-be06bf0906dd@embeddedor.com>
Date:   Fri, 15 Sep 2023 14:31:46 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kees Cook <keescook@...omium.org>, Alasdair Kergon <agk@...hat.com>
Cc:     Mike Snitzer <snitzer@...nel.org>, dm-devel@...hat.com,
        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] dm crypt: Annotate struct crypt_config with __counted_by



On 9/15/23 14:03, 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 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 crypt_config.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Alasdair Kergon <agk@...hat.com>
> Cc: Mike Snitzer <snitzer@...nel.org>
> Cc: dm-devel@...hat.com
> Signed-off-by: Kees Cook <keescook@...omium.org>

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

Thanks
-- 
Gustavo

> ---
>   drivers/md/dm-crypt.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index f2662c21a6df..f276e9460feb 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -224,7 +224,7 @@ struct crypt_config {
>   	struct mutex bio_alloc_lock;
>   
>   	u8 *authenc_key; /* space for keys in authenc() format (if used) */
> -	u8 key[];
> +	u8 key[] __counted_by(key_size);
>   };
>   
>   #define MIN_IOS		64