CVE-2022-23033

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2022-23033 / XSA-393 version 2 arm: guest_physmap_remove_page not removing the p2m mappings UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= The functions to remove one or more entries from a guest p2m pagetable on Arm (p2m_remove_mapping, guest_physmap_remove_page, and p2m_set_entry with mfn set to INVALID_MFN) do not actually clear the pagetable entry if the entry doesn’t have the valid bit set. It is possible to have a valid pagetable entry without the valid bit set when a guest operating system uses set/way cache maintenance instructions. For instance, a guest issuing a set/way cache maintenance instruction, then calling the XENMEM_decrease_reservation hypercall to give back memory pages to Xen, might be able to retain access to those pages even after Xen started reusing them for other purposes. IMPACT ====== A malicious guest may be able to access Xen and other domains’ memory. This could cause information leaks, host or domain Denial of Service (DoS), and privilege escalations. VULNERABLE SYSTEMS ================== Xen version 4.12 and newer are vulnerable. Only Arm systems are vulnerable. x86 systems are not vulnerable. MITIGATION ========== There is no known mitigation. CREDITS ======= This issue was discovered by Dmytro Firsov of EPAM. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. Note that patches for released versions are generally prepared to apply to the stable branches, and may not apply cleanly to the most recent release tarball. Downstreams are encouraged to update to the tip of the stable branch before applying these patches. xsa393.patch xen-unstable - Xen 4.12.x $ sha256sum xsa393* ccd746687c6080ec00ba363477d8815bc648d957c21c47d3a5330be9251806a4 xsa393.meta 89e5d66c437bacbe344e72d15720c1dde98dd97fab7184c7a6ff32bb63d442dd xsa393.patch $ DEPLOYMENT DURING EMBARGO ========================= Deployment of the patches and/or mitigations described above (or others which are substantially similar) is permitted during the embargo, even on public-facing systems with untrusted guest users and administrators. But: Distribution of updated software is prohibited (except to other members of the predisclosure list). Predisclosure list members who wish to deploy significantly different patches and/or mitigations, please contact the Xen Project Security Team. (Note: this during-embargo deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable. This is to enable the community to have oversight of the Xen Project Security Team’s decisionmaking.) For more information about permissible uses of embargoed information, consult the Xen Project community’s agreed Security Policy: http://www.xenproject.org/security-policy.html -----BEGIN PGP SIGNATURE----- iQFABAEBCAAqFiEEI+MiLBRfRHX6gGCng/4UyVfoK9kFAmHv38oMHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZfAcH/iXwGyTpGU7AIOGNGH1VYnn3FBAVBvT4etuPXO8o heX252xCZNh7M7qel/Db1aaAMpo2T2ypH02ZguKsojnoRAo4QrEjrnBGsCasfzqv HFd3nMlmksNlKI9xGPxt+Q6eNuoEHgu7i/7r3J2DgiC/Pa5Hw4SMF2eat7Er5zDL waDHFkiONa6LM/dtgZkkgps5d3B8cR4tXo3VDLzBC0pK3IysSLnacLy7FfvLg7c0 pc/qFvUXbsFjKVmG+EKu8VlCpkWONFP1FXC4pfM+rSjDdVhmc8FhFzOLzD6Tkptt MJhgOCMrO1Z//F07l0B9C9sxVi7K5mUDSWhonUQVPCWgl2s= =06Nb -----END PGP SIGNATURE-----