Subject: Re: [PATCH] firmware: imx: warn on unexpected RX

From: Shawn Guo <[email-masked]>
Date: Sun, 6 Oct 2019 08:57:30 +0800

On Wed, Sep 04, 2019 at 10:54:58AM +0300, Leonard Crestez wrote:
> The imx_scu_call_rpc function function returns the result inside the

s/function function/function

> 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

unexpected response

I fixed them up and applied the patch.

Shawn

> 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 <[email-masked]>
> ---
>  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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