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

[Pratyush Brahma]

On 2/13/2024 1:36 PM, Dmitry Baryshkov wrote:
> 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.
Haven't added as the patchset in-reply-to hasn't been merged to 
linux-next. Please refer my next reply.
> > ---
> >   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.
This is in reply to the patchset at: 
https://lore.kernel.org/all/20240201210529.7728-4-quic_c_gdjako@xxxxxxxxxxx
The aforementioned patchset introduces this bug. This is a suggested fix 
to the bug.
> > -       return &qsmmu->smmu;
> > +       return smmu;
> >   }
> >
> >   /* Implementation Defined Register Space 0 register offsets */
> > --
> > 2.17.1
Thanks,
Pratyush