linux-hardening - Re: [PATCH v2 2/3] spi: axi-spi-engine: use __counted

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Date: Mon, 4 Mar 2024 10:16:05 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: David Lechner <dlechner@...libre.com>, Mark Brown <broonie@...nel.org>
Cc: Michael Hennerich <michael.hennerich@...log.com>,
 Nuno Sá <nuno.sa@...log.com>,
 Kees Cook <keescook@...omium.org>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>, linux-spi@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 2/3] spi: axi-spi-engine: use __counted_by() attribute



On 04/03/24 10:04, David Lechner wrote:
> This adds the __counted_by() attribute to the flex array at the end of
> struct spi_engine_program in the AXI SPI Engine controller driver.
> 
> The assignment of the length field has to be reordered to be before
> the access to the flex array in order to avoid potential compiler
> warnings/errors due to adding the __counted_by() attribute.
> 
> Suggested-by: Nuno Sá <nuno.sa@...log.com>
> Signed-off-by: David Lechner <dlechner@...libre.com>

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

Thanks
--
Gustavo

> ---
> v2 changes:
> * Reordered assignment of length field.
> ---
>   drivers/spi/spi-axi-spi-engine.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
> index d89f75170c9e..a8f626165f44 100644
> --- a/drivers/spi/spi-axi-spi-engine.c
> +++ b/drivers/spi/spi-axi-spi-engine.c
> @@ -75,7 +75,7 @@
>   
>   struct spi_engine_program {
>   	unsigned int length;
> -	uint16_t instructions[];
> +	uint16_t instructions[] __counted_by(length);
>   };
>   
>   /**
> @@ -115,9 +115,10 @@ struct spi_engine {
>   static void spi_engine_program_add_cmd(struct spi_engine_program *p,
>   	bool dry, uint16_t cmd)
>   {
> -	if (!dry)
> -		p->instructions[p->length] = cmd;
>   	p->length++;
> +
> +	if (!dry)
> +		p->instructions[p->length - 1] = cmd;
>   }
>   
>   static unsigned int spi_engine_get_config(struct spi_device *spi)
>