ISSUE DESCRIPTION ================= Certain PV guest kernel operations (page table writes in particular) need emulation, and use Xen's general x86 instruction emulator. This allows a malicious guest kernel which asynchronously modifies its instruction stream to effect the clearing of EFLAGS.IF from the state used to return to guest context. IMPACT ====== A malicious guest kernel administrator can cause a host hang or crash, resulting in a Denial of Service. VULNERABLE SYSTEMS ================== All Xen versions are vulnerable. Only x86 PV guests can exploit the vulnerability. Neither ARM guests nor x86 HVM guests can exploit the vulnerability. MITIGATION ========== Running only HVM guests will avoid the vulnerability. For PV guests the vulnerability can be avoided if the guest kernel is controlled by the host rather than guest administrator, provided that further steps are taken to prevent the guest administrator from loading code into the kernel (e.g. by disabling loadable modules etc) or from using other mechanisms which allow them to run code at kernel privilege. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa202.patch xen-unstable, Xen 4.8.x, Xen 4.7.x xsa202-4.6.patch Xen 4.6.x, Xen 4.5.x xsa202-4.4.patch Xen 4.4.x $ sha256sum xsa202* 057be742acfef200ba6f094a5dce486dd1c4e15013afe3efc963523ce2ec9cbb xsa202.patch cd53dc8b761dc7eb60998ea2419c98af926aa62b4317dbef15f597f5554f9015 xsa202-4.4.patch e007187639f5392a9256979504d50eff0ae38309a61524ea42c4150fab38b6f4 xsa202-4.6.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deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable.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
@maintainer, please proceed.
commit 759e56ed0bd502aecb397a0e0d585e74b4447eb0 Author: Yixun Lan <dlan@gentoo.org> Date: Tue Dec 20 23:54:44 2016 +0800 app-emulation/xen: security bump, fix XSA-202,203,204 Gento-Bug: 601986, 601988 Package-Manager: Portage-2.3.3, Repoman-2.3.1 :100644 100644 24b2ee46aa... fd25026812... M app-emulation/xen/Manifest :000000 100644 0000000000... e077b5598a... A app-emulation/xen/xen-4.6.4-r4.ebuild :000000 100644 0000000000... e077b5598a... A app-emulation/xen/xen-4.7.1-r4.ebuild :100644 100644 ca48cdafac... 28479d7a29... R099 app-emulation/xen/xen-4.8.0.ebuild app-emulation/xen/xen-4.8.0-r1.ebuild https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=759e56ed0bd502aecb397a0e0d585e74b4447eb0
Arches, please test and mark stable: =app-emulation/xen-4.7.1-r4 Target keyword only: "amd64"
@ Maintainer(s): v4.6.x, which you also bumped to add the updated patch set, is also affected. Do you really want to stabilize only v4.7.x? So you are going to remove v4.6.x afterwards? Otherwise we need to stabilize =app-emulation/xen-4.6.4-r4 as well...
amd64 stable. Maintainer(s), please cleanup. Security, please vote.
@ Arches, maintainer(s) have decided to move to 4.7.x branch. Please stabilize =app-emulation/xen-pvgrub-4.7.1-r1 =app-emulation/xen-tools-4.7.1-r4 as well.
=app-emulation/xen-pvgrub-4.7.1-r1 stabilized. amd64 is good now.
x86 stable
Added to existing GLSA.
This issue was resolved and addressed in GLSA 201612-56 at https://security.gentoo.org/glsa/201612-56 by GLSA coordinator Thomas Deutschmann (whissi).
