Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
In the Linux kernel, the following vulnerability has been resolved:genirq/msi: Store the IOMMU IOVA directly in msi_desc instead of iommu_cookieThe IOMMU translation for MSI message addresses has been a 2-step process,separated in time: 1) iommu_dma_prepare_msi(): A cookie pointer containing the IOVA address is stored in the MSI descriptor when an MSI interrupt is allocated. 2) iommu_dma_compose_msi_msg(): this cookie pointer is used to compute a translated message address.This has an inherent lifetime problem for the pointer stored in the cookiethat must remain valid between the two steps. However, there is no lockingat the irq layer that helps protect the lifetime. Today, this works underthe assumption that the iommu domain is not changed while MSI interruptsbeing programmed. This is true for normal DMA API users within the kernel,as the iommu domain is attached before the driver is probed and cannot bechanged while a driver is attached.Classic VFIO type1 also prevented changing the iommu domain while VFIO wasrunning as it does not support changing the "container" after starting up.However, iommufd has improved this so that the iommu domain can be changedduring VFIO operation. This potentially allows userspace to directly raceVFIO_DEVICE_ATTACH_IOMMUFD_PT (which calls iommu_attach_group()) andVFIO_DEVICE_SET_IRQS (which calls into iommu_dma_compose_msi_msg()).This potentially causes both the cookie pointer and the unlocked call toiommu_get_domain_for_dev() on the MSI translation path to become UAFs.Fix the MSI cookie UAF by removing the cookie pointer. The translated IOVAaddress is already known during iommu_dma_prepare_msi() and cannot change.Thus, it can simply be stored as an integer in the MSI descriptor.The other UAF related to iommu_get_domain_for_dev() will be addressed inpatch "iommu: Make iommu_dma_prepare_msi() into a generic operation" byusing the IOMMU group mutex.
No PoCs from references.
- https://github.com/w4zu/Debian_security