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

[Robin Murphy]

On 2024-02-13 8:17 am, Pratyush Brahma wrote:
> 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.

Unless you are the 0-day bot, please just point out bugs in under-review 
patches via regular review comments rather than sending patches for 
unmerged patches.

There is nothing to fix in mainline, and as I commented on the binding 
patch I'm not sure I agree with the fundamental premise for touching 
qcom_smmu_create() in this series at all.

Thanks,
Robin.

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