RE: [PATCH] firmware: imx: warn on unexpected RX

[Anson Huang <anson.huang@nxp.com>]

> Subject: [PATCH] firmware: imx: warn on unexpected RX
> 
> The imx_scu_call_rpc function function returns the result inside the same
> "msg" struct containing the transmitted message. This is implemented by
> holding a pointer to msg (which is usually on the stack) in sc_imx_rpc and
> writing to it from imx_scu_rx_callback.
> 
> This means that if the have_resp parameter is incorrect or SCU sends an
> unexpected for any reason the most likely result is kernel stack corruption.
> 
> Fix this by only setting sc_imx_rpc.msg for the duration of the
> imx_scu_call_rpc call and warning in imx_scu_rx_callback if unset.
> 
> Print the unexpected response data to help debugging.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>

Acked-by: Anson Huang <Anson.Huang@nxp.com>

> ---
>  drivers/firmware/imx/imx-scu.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/imx/imx-scu.c b/drivers/firmware/imx/imx-
> scu.c index 04a24a863d6e..869be7a5172c 100644
> --- a/drivers/firmware/imx/imx-scu.c
> +++ b/drivers/firmware/imx/imx-scu.c
> @@ -105,10 +105,16 @@ static void imx_scu_rx_callback(struct mbox_client
> *c, void *msg)
>  	struct imx_sc_chan *sc_chan = container_of(c, struct imx_sc_chan,
> cl);
>  	struct imx_sc_ipc *sc_ipc = sc_chan->sc_ipc;
>  	struct imx_sc_rpc_msg *hdr;
>  	u32 *data = msg;
> 
> +	if (!sc_ipc->msg) {
> +		dev_warn(sc_ipc->dev, "unexpected rx idx %d 0x%08x,
> ignore!\n",
> +				sc_chan->idx, *data);
> +		return;
> +	}
> +
>  	if (sc_chan->idx == 0) {
>  		hdr = msg;
>  		sc_ipc->rx_size = hdr->size;
>  		dev_dbg(sc_ipc->dev, "msg rx size %u\n", sc_ipc->rx_size);
>  		if (sc_ipc->rx_size > 4)
> @@ -163,11 +169,12 @@ int imx_scu_call_rpc(struct imx_sc_ipc *sc_ipc,
> void *msg, bool have_resp)
>  		return -EINVAL;
> 
>  	mutex_lock(&sc_ipc->lock);
>  	reinit_completion(&sc_ipc->done);
> 
> -	sc_ipc->msg = msg;
> +	if (have_resp)
> +		sc_ipc->msg = msg;
>  	sc_ipc->count = 0;
>  	ret = imx_scu_ipc_write(sc_ipc, msg);
>  	if (ret < 0) {
>  		dev_err(sc_ipc->dev, "RPC send msg failed: %d\n", ret);
>  		goto out;
> @@ -185,10 +192,11 @@ int imx_scu_call_rpc(struct imx_sc_ipc *sc_ipc,
> void *msg, bool have_resp)
>  		hdr = msg;
>  		ret = hdr->func;
>  	}
> 
>  out:
> +	sc_ipc->msg = NULL;
>  	mutex_unlock(&sc_ipc->lock);
> 
>  	dev_dbg(sc_ipc->dev, "RPC SVC done\n");
> 
>  	return imx_sc_to_linux_errno(ret);
> --
> 2.17.1

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