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

[Pratyush Brahma <quic_pbrahma@quicinc.com>]

On 2/13/2024 1:36 PM, Dmitry Baryshkov wrote:
> On Tue, 13 Feb 2024 at 08:27, Pratyush Brahma <quic_pbrahma@quicinc.com> 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@quicinc.com>
> 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@quicinc.com
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