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Date:   Mon, 17 Jan 2022 11:25:51 -0700
From:   Mathieu Poirier <mathieu.poirier@linaro.org>
To:     "Peng Fan (OSS)" <peng.fan@oss.nxp.com>
Cc:     bjorn.andersson@linaro.org, shawnguo@kernel.org,
        s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com,
        linux-imx@nxp.com, linux-remoteproc@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Peng Fan <peng.fan@nxp.com>
Subject: Re: [PATCH] remoteproc: imx_rproc: validate resource table
Message-ID: <20220117182551.GC1119324@p14s>
References: <20220111033333.403448-1-peng.fan@oss.nxp.com>
 <20220111033333.403448-2-peng.fan@oss.nxp.com>
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In-Reply-To: <20220111033333.403448-2-peng.fan@oss.nxp.com>
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Good morning,

On Tue, Jan 11, 2022 at 11:33:23AM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@nxp.com>
> 
> Currently NXP use one device tree to support all NXP released Cortex-M
> demos. There is one simple demo that not need to communicate with
> Linux, thus it will not update the resource table. So there maybe
> garbage data in it. In such case, Linux should directly ignore it.
> 
> It is hard to decide what data is garbage data, NXP released SDK use
> ver(1), reserved(0) in a valid resource table. But in case others
> use different value, so here use 0xff as a max value for ver and num.
> 
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
>  drivers/remoteproc/imx_rproc.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/remoteproc/imx_rproc.c b/drivers/remoteproc/imx_rproc.c
> index 0bd24c937a73..75fde16f80a4 100644
> --- a/drivers/remoteproc/imx_rproc.c
> +++ b/drivers/remoteproc/imx_rproc.c
> @@ -490,11 +490,19 @@ static int imx_rproc_attach(struct rproc *rproc)
>  static struct resource_table *imx_rproc_get_loaded_rsc_table(struct rproc *rproc, size_t *table_sz)
>  {
>  	struct imx_rproc *priv = rproc->priv;
> +	struct resource_table *table;
>  
>  	/* The resource table has already been mapped in imx_rproc_addr_init */
>  	if (!priv->rsc_table)
>  		return NULL;
>  
> +	table = priv->rsc_table;
> +	/* Gabage data check */
> +	if (table->ver >= 0xff || table->num >= 0xff || table->reserved[0] || table->reserved[1]) {
> +		dev_err(priv->dev, "Ignore invalid rsc table\n");
> +		return NULL;
> +	}
> +

This seems like the wrong fix to me.  Either use different DTs or update the
resource table for all demos - efficiency should not be a problem since they are
demos.  With the above it is only a matter of time before the pattern
associated with valid resource tables changes, leading to more hacks that will be
impossible to maintain over time.

Thanks,
Mathieu

>  	*table_sz = SZ_1K;
>  	return (struct resource_table *)priv->rsc_table;
>  }
> -- 
> 2.25.1
>