CVE-2026-52952: iommu: Fix WARN_ON in __iommu_group_set_domain_nofail() due to reset

In the Linux kernel, the following vulnerability has been resolved:

iommu: Fix WARNON in iommugroupsetdomainnofail() due to reset

In iommugroupsetdomaininternal(), concurrent domain attachments are rejected when any device in the group is recovering. This is necessary to fence concurrent attachments to a multi-device group where devices might share the same RID due to PCI DMA alias quirks, but triggers the WARNON in iommugroupsetdomainnofail().

Other IOMMUSETDOMAINMUSTSUCCEED callers in detach/teardown paths, such as iommugroupsetcoredomain and iommureleasedmaownership, should not be rejected, as the domain would be freed anyway in these nofail paths while group->domain is still pointing to it. So pcidevresetiommudone() could trigger a UAF when re-attaching group->domain.

Honor the IOMMUSETDOMAINMUSTSUCCEED flag, allowing the callers through the group->recoverycnt fence, so as to update the group->domain pointer. Instead add a gdev->blocked check in the device iteration loop, to prevent any concurrent per-device detachment.