linux-kernel - Re: [PATCH] soc: imx: imx-scu: Getting UID from SCU should have response

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Message-ID: <VI1PR04MB7023B9C325C54AA8112F1AE5EEB80@VI1PR04MB7023.eurprd04.prod.outlook.com>
Date:   Wed, 4 Sep 2019 07:34:06 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     Anson Huang <anson.huang@....com>,
        Aisheng Dong <aisheng.dong@....com>
CC:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Daniel Baluta <daniel.baluta@....com>,
        Abel Vesa <abel.vesa@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH] soc: imx: imx-scu: Getting UID from SCU should have
 response

On 2019-09-04 10:14 AM, Anson Huang wrote:
> The SCU firmware API for getting UID should have response,
> otherwise, the message stored in function stack could be
> released and then the response data received from SCU will be
> stored into that released stack and cause kernel NULL pointer
> dump.

This fix looks good, but looking at imx-scu code it seems that passing 
the incorrect "have_resp" argument to imx_scu_call_rpc or just receiving 
an unexpected message from SCFW will always result in kernel stack 
corruption!

This is worth handling inside imx-scu itself: unless a response was 
explicitly requested it should ignore and print a warning on rx, for 
example by setting imx_sc_ipc to NULL when not waiting for a response.

Holding on to arbitrary stack pointers is bad.

--
Regards,
Leonard

> diff --git a/drivers/soc/imx/soc-imx-scu.c b/drivers/soc/imx/soc-imx-scu.c
> index 50831eb..c68882e 100644
> --- a/drivers/soc/imx/soc-imx-scu.c
> +++ b/drivers/soc/imx/soc-imx-scu.c
> @@ -46,7 +46,7 @@ static ssize_t soc_uid_show(struct device *dev,
>   	hdr->func = IMX_SC_MISC_FUNC_UNIQUE_ID;
>   	hdr->size = 1;
>   
> -	ret = imx_scu_call_rpc(soc_ipc_handle, &msg, false);
> +	ret = imx_scu_call_rpc(soc_ipc_handle, &msg, true);
>   	if (ret) {
>   		pr_err("%s: get soc uid failed, ret %d\n", __func__, ret);
>   		return ret;