Headline
CVE-2021-28700
xen/arm: No memory limit for dom0less domUs The dom0less feature allows an administrator to create multiple unprivileged domains directly from Xen. Unfortunately, the memory limit from them is not set. This allow a domain to allocate memory beyond what an administrator originally configured.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2021-28700 / XSA-383 version 2 xen/arm: No memory limit for dom0less domUs UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= The dom0less feature allows an administrator to create multiple unprivileged domains directly from Xen. Unfortunately, the memory limit from them is not set. This allow a domain to allocate memory beyond what an administrator originally configured. IMPACT ====== Malicious dom0less guest could drive Xen out of memory and may result to a Denial of Service (DoS) attack affecting the entire system. VULNERABLE SYSTEMS ================== Only Arm systems are vulnerable. Only domains created using the dom0less feature are affected. Only domains created using the dom0less feature can leverage the vulnerability. All versions of Xen since 4.12 are vulnerable. MITIGATION ========== There is no known mitigation. CREDITS ======= This issue was discovered by Julien Grall of Amazon. 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. xsa383.patch xen-unstable - Xen 4.13.x xsa383-4.12.patch Xen 4.12.x $ sha256sum xsa383* 773fe38d5d182ce43b5552fcdf6ed08c33126ed728e40d94c5050f89bfb3bd4d xsa383.meta cfd0632d250cc36d88269ae08e19e742c6bd07ba130c2604d51a10ba64d4e413 xsa383.patch d18f72fa595f330fa8ed13c9412a36fba58a8baf9ad30b9fc2fd4e4533c0ee1a xsa383-4.12.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/4UyVfoK9kFAmEmMPYMHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZmboIALCcOpac8K7jPXZ+D5S5S1kGExOHYCLDBCZ6LyPt jUmuR3r7xnkpJmcwSqGBHF5/PR6Sug+AjiggR8WHAFYiKod7yt1NjR4dm92Jy89x t4mpyQ2ZX7PIMOiTfxlsmzsDspBxjk9sV6Pt7w4o25MiWdmY41hEkE+qtJ0OBto0 btzbaInKko6SXZWPGGpAToKlKPnwcApe2DehGYO98xl8eUZ8Ql/1lieHjuSK60Nx RlboPeGDZwDgDroRj8GFNGxl2hESULVof0tG3w2IXPmYoa9iTKNUnO3KFL4kAJ/p ZWzyRuHbX9FjQXBFnJJ5pyTHrc1aYzXJCwxAoSt436aRX2c= =NGUO -----END PGP SIGNATURE-----
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