On 2023/9/11 14:57, Tian, Kevin wrote:
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?
I was concerned that when iommufd uses iopf, page fault report/response may occur simultaneously with enable/disable PRI. Currently, this is not an issue as the enable/disable PRI is in its own path. In the future, we may discard this interface and enable PRI when attaching the first PRI-capable domain, and disable it when detaching the last PRI-capable domain.
btw a Fix tag is required given this mislocking issue has been there for quite some time...
I don't see any real issue fixed by this change. It's only a lock refactoring after the code refactoring and preparing it for iommufd use. Perhaps I missed anything? Best regards, baolu
