linux-kernel - Re: [PATCH v2 1/2] remoteproc: qcom: Handle reserved-memory allocation issues

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Date:   Thu, 15 Jun 2023 11:44:06 +0100
From:   Caleb Connolly <caleb.connolly@...aro.org>
To:     Stephan Gerhold <stephan@...hold.net>,
        Bjorn Andersson <andersson@...nel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] remoteproc: qcom: Handle reserved-memory
 allocation issues



On 6/14/23 17:31, Stephan Gerhold wrote:
> If Linux fails to allocate the dynamic reserved memory specified in the
> device tree, the size of the reserved_mem will be 0. Add a check for
> this to avoid using an invalid reservation.
> 
> Signed-off-by: Stephan Gerhold <stephan@...hold.net>

Other uses of of_reserved_mem_lookup() also have unchecked uses of rmem 
[1], or check different things [2].

Does it make sense to put this check in the function itself?

I can't think of any obvious scenarios where it makes sense to 
differentiate between rmem being NULL vs having a size of zero at the 
time where a driver is fetching it.

As Bjorn described in the rmtfs patch, the memory allocation is 
essentially ignored, wouldn't it be better to print an error and 
invalidate the rmem in [3]?

[1]: 
https://elixir.bootlin.com/linux/v6.4-rc6/source/drivers/net/ethernet/mediatek/mtk_wed.c#L818
[2]: 
https://elixir.bootlin.com/linux/v6.4-rc6/source/drivers/remoteproc/rcar_rproc.c#L71
[3]: 
https://elixir.bootlin.com/linux/v6.4-rc6/source/drivers/of/of_reserved_mem.c#L276

// Caleb (they/them)
> ---
> New patch in v2, I wasn't aware of this until Bjorn posted a similar
> patch for rmtfs:
> https://lore.kernel.org/linux-arm-msm/20230530233643.4044823-4-quic_bjorande@quicinc.com/
> ---
>   drivers/remoteproc/qcom_q6v5_mss.c  | 2 +-
>   drivers/remoteproc/qcom_q6v5_wcss.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/remoteproc/qcom_q6v5_mss.c b/drivers/remoteproc/qcom_q6v5_mss.c
> index 70bffc9f33f6..a35ab6e860f3 100644
> --- a/drivers/remoteproc/qcom_q6v5_mss.c
> +++ b/drivers/remoteproc/qcom_q6v5_mss.c
> @@ -1932,7 +1932,7 @@ static int q6v5_alloc_memory_region(struct q6v5 *qproc)
>   		return 0;
>   
>   	rmem = of_reserved_mem_lookup(node);
> -	if (!rmem) {
> +	if (!rmem || !rmem->size) {
>   		dev_err(qproc->dev, "unable to resolve metadata region\n");
>   		return -EINVAL;
>   	}
> diff --git a/drivers/remoteproc/qcom_q6v5_wcss.c b/drivers/remoteproc/qcom_q6v5_wcss.c
> index b437044aa126..9edab9d60c21 100644
> --- a/drivers/remoteproc/qcom_q6v5_wcss.c
> +++ b/drivers/remoteproc/qcom_q6v5_wcss.c
> @@ -882,7 +882,7 @@ static int q6v5_alloc_memory_region(struct q6v5_wcss *wcss)
>   		rmem = of_reserved_mem_lookup(node);
>   	of_node_put(node);
>   
> -	if (!rmem) {
> +	if (!rmem || !rmem->size) {
>   		dev_err(dev, "unable to acquire memory-region\n");
>   		return -EINVAL;
>   	}
>