linux-kernel - Re: [PATCH V2] mailbox: imx-mailbox: fix scu msg header size check

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Date:   Wed, 15 Apr 2020 07:55:02 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     peng.fan@....com
Cc:     shawnguo@...nel.org, s.hauer@...gutronix.de,
        jassisinghbrar@...il.com, leonard.crestez@....com,
        kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        Anson.Huang@....com, aisheng.dong@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] mailbox: imx-mailbox: fix scu msg header size check

On Tue, Apr 14, 2020 at 09:21:15PM +0800, peng.fan@....com wrote:
> From: Peng Fan <peng.fan@....com>
> 
> The i.MX8 SCU message header size is the number of "u32" elements,
> not "u8", so fix the check.
> 
> Reported-by: coverity-bot <keescook+coverity-bot@...omium.org>
> Addresses-Coverity-ID: 1461658 ("Memory - corruptions")
> Signed-off-by: Peng Fan <peng.fan@....com>

Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>

Measuring size in mailboxes instead of bytes is really challenging :) I
would expect similar issues on other places as well.

Regards,
Oleksij

> ---
> 
> V2:
>  Drop parenthesis, add comment, update err msg.
> 
>  drivers/mailbox/imx-mailbox.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mailbox/imx-mailbox.c b/drivers/mailbox/imx-mailbox.c
> index 7906624a731c..fd3a9a60416d 100644
> --- a/drivers/mailbox/imx-mailbox.c
> +++ b/drivers/mailbox/imx-mailbox.c
> @@ -154,12 +154,17 @@ static int imx_mu_scu_tx(struct imx_mu_priv *priv,
>  
>  	switch (cp->type) {
>  	case IMX_MU_TYPE_TX:
> -		if (msg->hdr.size > sizeof(*msg)) {
> +		/*
> +		 * msg->hdr.size specifies the number of u32 words while
> +		 * sizeof yields bytes.
> +		 */
> +
> +		if (msg->hdr.size > sizeof(*msg) / 4) {
>  			/*
>  			 * The real message size can be different to
>  			 * struct imx_sc_rpc_msg_max size
>  			 */
> -			dev_err(priv->dev, "Exceed max msg size (%zu) on TX, got: %i\n", sizeof(*msg), msg->hdr.size);
> +			dev_err(priv->dev, "Maximal message size (%zu bytes) exceeded on TX; got: %i bytes\n", sizeof(*msg), msg->hdr.size << 2);
>  			return -EINVAL;
>  		}
>  
> @@ -198,9 +203,8 @@ static int imx_mu_scu_rx(struct imx_mu_priv *priv,
>  	imx_mu_xcr_rmw(priv, 0, IMX_MU_xCR_RIEn(0));
>  	*data++ = imx_mu_read(priv, priv->dcfg->xRR[0]);
>  
> -	if (msg.hdr.size > sizeof(msg)) {
> -		dev_err(priv->dev, "Exceed max msg size (%zu) on RX, got: %i\n",
> -			sizeof(msg), msg.hdr.size);
> +	if (msg.hdr.size > sizeof(msg) / 4) {
> +		dev_err(priv->dev, "Maximal message size (%zu bytes) exceeded on RX; got: %i bytes\n", sizeof(msg), msg.hdr.size << 2);
>  		return -EINVAL;
>  	}
>  
> -- 
> 2.16.4
> 
> 

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