[PATCH] iommu/arm-smmu-qcom: NULL pointer check for driver data

[Rob Clark]

On Wed, Aug 16, 2023 at 3:55 PM Aravind Vijayakumar
<quic_aprasann at quicinc.com> wrote:
>
> The driver_data is NULL when qcom_adreno_smmu_init_context()
> is called before the dev_set_drvdata() from the client driver
> and is resulting in kernel crash.
>
> So add a null pointer check to handle the scenario
> where the client driver for the GPU SMMU device would
> be setting the driver data after the smmu client device
> probe is done and not necessarily before that. The function
> qcom_adreno_smmu_init_context() assumes that the client
> driver always set the driver data using dev_set_drvdata()
> before the smmu client device probe, but this assumption
> is not always true.
>
> Signed-off-by: Aravind Vijayakumar <quic_aprasann at quicinc.com>
> ---
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index c71afda79d64..5323f82264ca 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -231,6 +231,9 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>          */
>
>         priv = dev_get_drvdata(dev);
> +       if (!priv)
> +               return 0;

could this -EPROBE_DEFER instead, or something like that?  I think you
patch as proposed would result in per-process gpu pgtables silently
failing

BR,
-R

> +
>         priv->cookie = smmu_domain;
>         priv->get_ttbr1_cfg = qcom_adreno_smmu_get_ttbr1_cfg;
>         priv->set_ttbr0_cfg = qcom_adreno_smmu_set_ttbr0_cfg;
> --
> 2.40.1
>