Date: Tue, 05 Apr 2022 12:00:29 +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 399 v2 (CVE-2022-26357) - race in VT-d domain ID cleanup -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2022-26357 / XSA-399 version 2 race in VT-d domain ID cleanup UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= Xen domain IDs are up to 15 bits wide. VT-d hardware may allow for only less than 15 bits to hold a domain ID associating a physical device with a particular domain. Therefore internally Xen domain IDs are mapped to the smaller value range. The cleaning up of the housekeeping structures has a race, allowing for VT-d domain IDs to be leaked and flushes to be bypassed. IMPACT ====== The precise impact is system specific, but would typically be a Denial of Service (DoS) affecting the entire host. Privilege escalation and information leaks cannot be ruled out. VULNERABLE SYSTEMS ================== Xen versions 4.11 through 4.16 are vulnerable. Xen versions 4.10 and earlier are not vulnerable. Only x86 systems with VT-d IOMMU hardware are vulnerable. Arm systems as well as x86 systems without VT-d hardware or without any IOMMUs in use are not vulnerable. Only x86 guests which have physical devices passed through to them can leverage the vulnerability. MITIGATION ========== Not passing through physical devices to untrusted guests will avoid the vulnerability. CREDITS ======= This issue was discovered by Jan Beulich of SUSE. 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. xsa399.patch xen-unstable xsa399-4.16.patch Xen 4.16.x - Xen 4.13.x xsa399-4.12.patch Xen 4.12.x $ sha256sum xsa399* 53b9745564eb21f70dbb7bd7194ff3518f29cd9715c68e9dd7eff25812968019 xsa399.patch 16c3327a60d8ab6c3524f10f57d63efaf2e3e54b807bc285a749cd1a94392a30 xsa399-4.12.patch 79d0f5a0442dec0a806d77a722a1d2c04793572fe0b564bf86dcd1c6d992a679 xsa399-4.16.patch $ DEPLOYMENT DURING EMBARGO ========================= Deployment of the patches described above (or others which are substantially similar) is permitted during the embargo, even on public-facing systems with untrusted guest users and administrators. HOWEVER, deployment of the mitigation is NOT permitted (except where all the affected systems and VMs are administered and used only by organisations which are members of the Xen Project Security Issues Predisclosure List). Specifically, deployment on public cloud systems is NOT permitted. This is because removal of pass-through devices or their replacement by emulated devices is a guest visible configuration change, which may lead to re-discovery of the issue. Deployment of this mitigation is permitted only AFTER the embargo ends. AND: 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/4UyVfoK9kFAmJMJDcMHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZpo8H/AqiAS0l5WJWl00bTQ4Q69REzd83m9Y3+UnUqRaf JUFWo4R1m4V2zJlq0E3TR/2ZS1RkXFJxlmXQyzueFmDEvMV2oKB0ids5ta1oUO2E eiQxdSFbTLrLnhI+4IxbTHHy+ovSHT/SKPeo1Zd1tXHfZ35g1OgGTYHHqj7RKJHp SyZT4iuAKjIr61M4NBKJcycpfRidlXEDvAotDX3jBQ06t3vgs/12nwe5LzzeV2V4 sIDjpeDGNKzgT2NgLP2b+XMEUg1259iWb19tS3PPNJaLKSvQqTBOFjK+sqh7ACXV v6ph2Yy0Q/ZP+N9DvCeBCPEU9A9RhmPYzobU+Lc/T85SrQ4= =sp/Q -----END PGP SIGNATURE----- Download attachment "xsa399.patch" of type "application/octet-stream" (1759 bytes) Download attachment "xsa399-4.12.patch" of type "application/octet-stream" (1765 bytes) Download attachment "xsa399-4.16.patch" of type "application/octet-stream" (1762 bytes)
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