linux-kernel - Re: [PATCH v3 3/3] soc: qcom: rtmfs: Handle reserved-memory allocation issues

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Date:   Thu, 21 Sep 2023 19:44:58 -0700
From:   Bjorn Andersson <andersson@...nel.org>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Caleb Connolly <caleb.connolly@...aro.org>
Subject: Re: [PATCH v3 3/3] soc: qcom: rtmfs: Handle reserved-memory
 allocation issues

On Thu, Sep 21, 2023 at 08:11:23PM +0200, Stephan Gerhold wrote:
> On Wed, Sep 20, 2023 at 07:37:32PM -0700, Bjorn Andersson wrote:
> > In the even that Linux failed to allocate the reserved memory range
> > specified in the DeviceTree, the size of the reserved_mem will be 0,
> > which results in a oops when memory remapping is attempted.
> > 
> > Detect this and report that the memory region was not found instead.
> > 
> > Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> 
> I dropped these checks in my remoteproc patches because Caleb suggested
> maybe putting this check directly in of_reserved_mem_lookup() (or
> similar) given that almost none of the users verify this [1].
> 
> Do you have any opinion on that? I asked back then too but you did not
> reply yet [2]. :-)
> 

I'm struggling to come up with a use case where one would like to get
hold of the rmem when it wasn't properly initialized. So, let's make an
attempt at returning NULL from of_reserved_mem_lookup() instead.

Thanks,
Bjorn

> [1]: https://lore.kernel.org/linux-arm-msm/c3f59fb4-4dd8-f27a-d3f5-b1870006a75c@linaro.org/
> [2]: https://lore.kernel.org/linux-arm-msm/ZIsld-MAdkKvdzTx@gerhold.net/
> 
> > ---
> >  drivers/soc/qcom/rmtfs_mem.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/soc/qcom/rmtfs_mem.c b/drivers/soc/qcom/rmtfs_mem.c
> > index 83bba9321e72..13823abd85c2 100644
> > --- a/drivers/soc/qcom/rmtfs_mem.c
> > +++ b/drivers/soc/qcom/rmtfs_mem.c
> > @@ -180,7 +180,7 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
> >  	int ret, i;
> >  
> >  	rmem = of_reserved_mem_lookup(node);
> > -	if (!rmem) {
> > +	if (!rmem || !rmem->size) {
> >  		dev_err(&pdev->dev, "failed to acquire memory region\n");
> >  		return -EINVAL;
> >  	}
> > 
> > -- 
> > 2.25.1
> >