linux-kernel - Re: [PATCH] soc: qcom: rpmh-rsc: Set suppress_bind

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Message-ID: <a429dfbb-4125-6019-c102-d5b2f4d7379f@codeaurora.org>
Date:   Mon, 22 Jun 2020 17:09:24 +0530
From:   Maulik Shah <mkshah@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>, agross@...nel.org,
        bjorn.andersson@...aro.org
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        dianders@...omium.org, rnayak@...eaurora.org, ilina@...eaurora.org,
        lsrao@...eaurora.org, john.stultz@...aro.org
Subject: Re: [PATCH] soc: qcom: rpmh-rsc: Set suppress_bind_attrs flag

Hi,

Thanks for the review Stephen.

On 6/22/2020 2:33 PM, Stephen Boyd wrote:
> Quoting Maulik Shah (2020-06-21 23:53:25)
>> rpmh-rsc driver is fairly core to system and should not be removable
>> once its probed. However it allows to unbind driver from sysfs using
>> below command which results into a crash on sc7180.
> What is the crash? The world falls apart because rpmh APIs start
> referencing pointers that point to freed memory?
Yes.
>
>> echo 18200000.rsc > /sys/bus/platform/drivers/rpmh/unbind
>>
>> Lets prevent unbind at runtime by setting suppress_bind_attrs flag.
> Ok. But when the Android module brigade comes knocking they'll have to
> revert this change and solve this problem too. Have fun!

No should not need to revert this change.

Even if rpmh-rsc is planned to be loadable module for android, Once 
loaded it should be disallowed to be removed.

same is the case for PDC irqchip as well. these drivers are core to the 
system and shouldn't be allowed to rmmod/unbind.

Thanks,
Maulik

>
>> Signed-off-by: Maulik Shah <mkshah@...eaurora.org>
>> ---
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>

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