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

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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: 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.


-       return &qsmmu->smmu;
+       return smmu;

  /* Implementation Defined Register Space 0 register offsets */


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