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Xen Security Advisory 372 v3 (CVE-2021-28693) - xen/arm: Boot modules are not scrubbed

To: xen-announce@xxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxx, xen-users@xxxxxxxxxxxxx, oss-security@xxxxxxxxxxxxxxxxxx

From: Xen.org security team <security@xxxxxxx>

Date: Tue, 08 Jun 2021 17:04:28 +0000

Cc: Xen.org security team <security-team-members@xxxxxxx>

Delivery-date: Tue, 08 Jun 2021 17:05:09 +0000

List-id: "Xen announcements $low volume$" <xen-announce.lists.xenproject.org>

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2021-28693 / XSA-372 version 3 xen/arm: Boot modules are not scrubbed UPDATES IN VERSION 3 ==================== Public release. ISSUE DESCRIPTION ================= The bootloader will load boot modules (e.g. kernel, initramfs...) in a temporary area before they are copied by Xen to each domain memory. To ensure sensitive data is not leaked from the modules, Xen must "scrub" them before handing the page over to the allocator. Unfortunately, it was discovered that modules will not be scrubbed on Arm. IMPACT ====== Sensitive information from the boot modules might be visible to another domain after boot. VULNERABLE SYSTEMS ================== Only Arm systems are vulnerable. System running with "bootscrub=off" (disabling boot scrubbing) are not vulnerable. All versions of Xen since 4.12 are vulnerable. MITIGATION ========== There is no mitigation available. CREDITS ======= This issue was discovered by Julien Grall of Amazon. RESOLUTION ========== Applying the appropriate set of attached patches 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. xsa372/*.patch xen-unstable xsa372-4.15/*.patch Xen 4.15.x xsa372-4.14/*.patch Xen 4.14.x - Xen 4.13.x xsa372-4.12/*.patch Xen 4.12.x $ sha256sum xsa372* xsa372*/* 06e43684c2d8a3085d55b8b40f57e1b9f1ee47519fac844dcbc21b57fb039915 xsa372.meta 8f872c7abe6c795dbef2e401f2223fda0dbb9d7c57dfebd8047eef37e1caf952 xsa372-4.12/0001-xen-arm-Create-dom0less-domUs-earlier.patch a43c6c11481cc3f13900908cee79cc6c5401921f6f4e8858c0796cf301cfe923 xsa372-4.12/0002-xen-arm-Boot-modules-should-always-be-scrubbed-if-bo.patch 6d1fad53795ebd251520022b6be901215426ba78ccbbc075841698973b74d2a2 xsa372-4.14/0001-xen-arm-Create-dom0less-domUs-earlier.patch 2ceb5d4d8d4f8a18046721daa3bb29633a620c4794b54e1265f5d4d69a314c3b xsa372-4.14/0002-xen-arm-Boot-modules-should-always-be-scrubbed-if-bo.patch 7feae5f9f7f2df0ec38c0b9358dc32671a9955f966b3120e17bb3fd820ce33ff xsa372-4.15/0001-xen-arm-Create-dom0less-domUs-earlier.patch 0cc73b4751fa49f68c6584b1c7882606c6e1f18561d8a6547017ab068de4eb4b xsa372-4.15/0002-xen-arm-Boot-modules-should-always-be-scrubbed-if-bo.patch 950672405c695ebf6ae59eebeb454bc0738b7afc3efa35ef9680d76eef4d4ec0 xsa372/0001-xen-arm-Create-dom0less-domUs-earlier.patch 9ceccd39c795e7756052a2f00256e043c8dda42e2c691df30e3f8b59190d6e8e xsa372/0002-xen-arm-Boot-modules-should-always-be-scrubbed-if-bo.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/4UyVfoK9kFAmC/oxIMHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZmdYIAMlZ2woM1hnb97BytpKkRM3v8AnyP4xhm29OoVI+ eaclrapZBPxi8qxv0+fxhe/2/t9gf98miEJftI8VRz5btiStmsgIjlEXUGpC6iwE u7HmLzu7QBX7r2FzpSTFnVVdbFwXCU3scYuO4qM8frCpxH4kevSSxPrT5E/oFVvA Y83ux8aKg041WTVQvK0gEVA7CgRVoxmbiYeag2JIaRGt8WnEKprbmGWQ5+DYq+pr 8tsLppHtyxppqSa7d6L67xdiNoRqAacfIezNFTpSIdyfS1m0QIIAJTr6Bg7Fd6zi F2AYcoZiNO53OSnobH3c64axIc5iBINZeXisVMnTDzKU3XE= =eQ/r -----END PGP SIGNATURE-----

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