Date: Tue, 14 Jun 2022 18:26:37 +0000 From: Xen.org security team <security@....org> To: xen-announce@...ts.xen.org, xen-devel@...ts.xen.org, xen-users@...ts.xen.org, oss-security@...ts.openwall.com CC: Xen.org security team <security-team-members@....org> Subject: Xen Security Advisory 404 v1 (CVE-2022-21123,CVE-2022-21124,CVE-2022-21166) - x86: MMIO Stale Data vulnerabilities -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2022-21123,CVE-2022-21124,CVE-2022-21166 / XSA-404 x86: MMIO Stale Data vulnerabilities ISSUE DESCRIPTION ================= This issue is related to the SRBDS, TAA and MDS vulnerabilities. Please see: https://xenbits.xen.org/xsa/advisory-320.html (SRBDS) https://xenbits.xen.org/xsa/advisory-305.html (TAA) https://xenbits.xen.org/xsa/advisory-297.html (MDS) Please see Intel's whitepaper: https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/technical-documentation/processor-mmio-stale-data-vulnerabilities.html IMPACT ====== An attacker might be able to directly read or infer data from other security contexts in the system. This can include data belonging to other VMs, or to Xen itself. The degree to which an attacker can obtain data depends on the CPU, and the system configuration. VULNERABLE SYSTEMS ================== Systems running all versions of Xen are affected. Only x86 processors are vulnerable. Processors from other manufacturers (e.g. ARM) are not believed to be vulnerable. Only Intel based processors are affected. Processors from other x86 manufacturers (e.g. AMD) are not believed to be vulnerable. Please consult the Intel Security Advisory for details on the affected processors and configurations. Per Xen's support statement, PCI passthrough should be to trusted domains because the overall system security depends on factors outside of Xen's control. As such, Xen, in a supported configuration, is not vulnerable to DRPW/SBDR. MITIGATION ========== All mitigations depend on functionality added in the IPU 2022.1 (May 2022) microcode release from Intel. Consult your dom0 OS vendor. To the best of the security team's understanding, the summary is as follows: Server CPUs (Xeon EP/EX, Scalable, and some Atom servers), excluding Xeon E3 (which use the client CPU design), are potentially vulnerable to DRPW (CVE-2022-21166). Client CPUs (inc Xeon E3) are, furthermore, potentially vulnerable to SBDR (CVE-2022-21123) and SBDS (CVE-2022-21125). SBDS only affects CPUs vulnerable to MDS. On these CPUs, there are previously undiscovered leakage channels. There is no change to the existing MDS mitigations. DRPW and SBDR only affects configurations where less privileged domains have MMIO mappings of buggy endpoints. Consult your hardware vendor. In configurations where less privileged domains have MMIO access to buggy endpoints, `spec-ctrl=unpriv-mmio` can be enabled which will cause Xen to mitigate cross-domain fill buffer leakage, and extend SRBDS protections to protect RNG data from leakage. 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. The patches are still under review. An update will be sent once they are reviewed and the backports are done. xsa404/xsa404-?.patch xen-unstable $ sha256sum xsa404*/* 18b307c2cbbd08d568e9dcb2447901d94e22ff1e3945c3436173aa693f6456fb xsa404/xsa404-1.patch d6f193ad963396285e983aa1c18539f67222582711fc62105c21b71b3b53a97d xsa404/xsa404-2.patch d2c123ccdf5eb9f862d6e9cb0e59045ae18799a07db149c7d90e301ca20436aa xsa404/xsa404-3.patch $ NOTE CONCERNING CVE-2022-21127 / Update to SRBDS ================================================ An issue was discovered with the SRBDS microcode mitigation. A microcode update was released as part of Intel's IPU 2022.1 in May 2022. Updating microcode is sufficient to fix the issue, with no extra actions required on Xen's behalf. Consult your dom0 OS vendor or OEM for updated microcode. NOTE CONCERNING CVE-2022-21180 / Undefined MMIO Hang ==================================================== A related issue was discovered. See: https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/advisory-guidance/undefined-mmio-hang.html Xen is not vulnerable to UMH in supported configurations. The only mitigation to is avoid passing impacted devices through to untrusted guests. -----BEGIN PGP SIGNATURE----- iQFABAEBCAAqFiEEI+MiLBRfRHX6gGCng/4UyVfoK9kFAmKo0Z0MHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZc8cH/RFgxQ4L8OewWMxsuowpgLg8NVyYGFMBgttscBh+ ANpjRTnV4yQGpt9nNFDAcXT1c/fvWhypOiwadEtczRl5k/Q96JOKFdiAc1QR35Oj vmbCLgO20jQ/GdTzaqKUaGBwi8GLShJvH1zMPJ2KuXk5w5uFDhj2gEiB6Kdv9+9O 4FBxQkpDzll0gs5v16ien8btKhEuZj9lNtzXZw5j4+DJD69MvQqsRPVdEt+M17Ox XGYcpfpLeGUaIUPFTPZDcFIJnMvqPBQyt+2eaeR2ezW2ouNpxepCSPsEDlAmSZ/K uZA0ShyJD3pfCxjc8eztyF/4zajY5EvuEtWdUZC/3zVaUec= =4EdA -----END PGP SIGNATURE----- Download attachment "xsa404/xsa404-1.patch" of type "application/octet-stream" (9496 bytes) Download attachment "xsa404/xsa404-2.patch" of type "application/octet-stream" (5116 bytes) Download attachment "xsa404/xsa404-3.patch" of type "application/octet-stream" (8009 bytes)
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