CVE-2024-41070

/// Technical description

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

KVM: PPC: Book3S HV: Prevent UAF in kvm_spapr_tce_attach_iommu_group()

Al reported a possible use-after-free (UAF) in kvm_spapr_tce_attach_iommu_group().

It looks up `stt` from tablefd, but then continues to use it after doing

fdput() on the returned fd. After the fdput() the tablefd is free to be

closed by another thread. The close calls kvm_spapr_tce_release() and

then release_spapr_tce_table() (via call_rcu()) which frees `stt`.

Although there are calls to rcu_read_lock() in

kvm_spapr_tce_attach_iommu_group() they are not sufficient to prevent

the UAF, because `stt` is used outside the locked regions.

With an artifcial delay after the fdput() and a userspace program which

triggers the race, KASAN detects the UAF:

BUG: KASAN: slab-use-after-free in kvm_spapr_tce_attach_iommu_group+0x298/0x720 [kvm]

Read of size 4 at addr c000200027552c30 by task kvm-vfio/2505

CPU: 54 PID: 2505 Comm: kvm-vfio Not tainted 6

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References