RE: [PATCH v4 09/10] iommu: Make iommu_queue_iopf() more generic

[Tian, Kevin]

> From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Tuesday, September 5, 2023 1:24 PM
> 
> Hi Kevin,
> 
> I am trying to address this issue in below patch. Does it looks sane to
> you?
> 
> iommu: Consolidate per-device fault data management
> 
> The per-device fault data is a data structure that is used to store
> information about faults that occur on a device. This data is allocated
> when IOPF is enabled on the device and freed when IOPF is disabled. The
> data is used in the paths of iopf reporting, handling, responding, and
> draining.
> 
> The fault data is protected by two locks:
> 
> - dev->iommu->lock: This lock is used to protect the allocation and
>    freeing of the fault data.
> - dev->iommu->fault_parameter->lock: This lock is used to protect the
>    fault data itself.
> 
> Improve the iopf code to enforce this lock mechanism and add a reference
> counter in the fault data to avoid use-after-free issue.
> 

Can you elaborate the use-after-free issue and why a new user count
is required?

btw a Fix tag is required given this mislocking issue has been there for
quite some time...