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Date:   Fri, 1 Jul 2022 10:42:12 +0100
From:   Sudeep Holla <sudeep.holla@arm.com>
To:     huhai <15815827059@163.com>
Cc:     cristian.marussi@arm.com, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, luriwen@kylinos.cn,
        liuyun01@kylinos.cn, huhai <huhai@kylinos.cn>,
        k2ci <kernel-bot@kylinos.cn>
Subject: Re: [PATCH] firmware: arm_scpi: Fix error handle when scpi probe
 failed
Message-ID: <20220701094212.snsnbdjc7hia5oti@bogus>
References: <20220701061606.151366-1-15815827059@163.com>
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On Fri, Jul 01, 2022 at 02:16:06PM +0800, huhai wrote:
> From: huhai <huhai@kylinos.cn>
>
> When scpi probe fails, do not just return the error code, but also reset
> the global scpi_info to NULL, otherwise scpi_hwmon_probe() may get a UAF
> and cause panic:
>

Interesting, which platform are you using this on ? SCPI is deprecated for
a while, please switch to SCMI which is well maintained both in terms of
specification and support in the kernel. I also assume this is 64-bit
platform, so I don't want you to get stuck in future because of lack
of some feature in SCPI. Please see if you can migrate to SCMI.

>   scpi_protocol FTSC0001:00: incorrect or no SCP firmware found
>   ... ...
>   Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
>   Mem abort info:
>

[...]

I think we don't see to make it complex. Can't it be as simple as:

Regards,
Sudeep

-->8

diff --git i/drivers/firmware/arm_scpi.c w/drivers/firmware/arm_scpi.c
index ddf0b9ff9e15..6fa1a5b193b8 100644
--- i/drivers/firmware/arm_scpi.c
+++ w/drivers/firmware/arm_scpi.c
@@ -799,7 +799,7 @@ static struct scpi_ops scpi_ops = {

 struct scpi_ops *get_scpi_ops(void)
 {
-       return scpi_info ? scpi_info->scpi_ops : NULL;
+       return scpi_info && scpi_info->scpi_ops ? scpi_info->scpi_ops : NULL;
 }
 EXPORT_SYMBOL_GPL(get_scpi_ops);