Re: [PATCH 1/1] iommu/arm-smmu-qcom: Fix use-after-free issue in qcom_smmu_create()

[Dmitry Baryshkov]

On Tue, 13 Feb 2024 at 08:27, Pratyush Brahma <quic_pbrahma@xxxxxxxxxxx> wrote:
>
> Currently, during arm smmu probe, struct arm_smmu_device pointer
> is allocated. The pointer is reallocated to a new struct qcom_smmu in
> qcom_smmu_create() with devm_krealloc() which frees the smmu device
> after copying the data into the new pointer.
>
> The freed pointer is then passed again in devm_of_platform_populate()
> inside qcom_smmu_create() which causes a use-after-free issue.
>
> Fix the use-after-free issue by reassigning the old pointer to
> the new pointer where the struct was copied by devm_krealloc().
>
> Signed-off-by: Pratyush Brahma <quic_pbrahma@xxxxxxxxxxx>

Missing Fixes tag.

> ---
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index ed5ed5da7740..49eaeed6a91c 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -710,6 +710,7 @@ static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,
>         qsmmu = devm_krealloc(smmu->dev, smmu, sizeof(*qsmmu), GFP_KERNEL);
>         if (!qsmmu)
>                 return ERR_PTR(-ENOMEM);
> +       smmu = &qsmmu->smmu;
>
>         qsmmu->smmu.impl = impl;
>         qsmmu->data = data;
> @@ -719,7 +720,7 @@ static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,
>         if (ret)
>                 return ERR_PTR(ret);

What is the tree that you have been developing this against? I don't
see this part of the code in the linux-next.

>
> -       return &qsmmu->smmu;
> +       return smmu;
>  }
>
>  /* Implementation Defined Register Space 0 register offsets */
> --
> 2.17.1
>
>


-- 
With best wishes
Dmitry