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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2020.2444 Xen Security Advisory XSA-329 17 July 2020 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Xen Publisher: Xen Operating System: Virtualisation UNIX variants (UNIX, Linux, OSX) Impact/Access: Unauthorised Access -- Existing Account Resolution: Patch/Upgrade Original Bulletin: http://xenbits.xen.org/xsa/advisory-329.html - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory XSA-329 version 2 Linux ioperm bitmap context switching issues UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= Linux 5.5 overhauled the internal state handling for the iopl() and ioperm() system calls. Unfortunately, one aspect on context switch wasn't wired up correctly for the Xen PVOps case. IMPACT ====== IO port permissions don't get rescinded when context switching to an unprivileged task. Therefore, all userspace can use the IO ports granted to the most recently scheduled task with IO port permissions. VULNERABLE SYSTEMS ================== Only x86 guests are vulnerable. All versions of Linux from 5.5 are potentially vulnerable. Linux is only vulnerable when running as x86 PV guest. Linux is not vulnerable when running as an x86 HVM/PVH guests. The vulnerability can only be exploited in domains which have been granted access to IO ports by Xen. This is typically only the hardware domain, and guests configured with PCI Passthrough. MITIGATION ========== Running only HVM/PVH guests avoids the vulnerability. CREDITS ======= This issue was discovered by Andy Lutomirski. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa329.patch Linux 5.5 and later $ sha256sum xsa329* cdb5ac9bfd21192b5965e8ec0a1c4fcf12d0a94a962a8158cd27810e6aa362f0 xsa329.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/4UyVfoK9kFAl8QU6EMHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZ/sEIAMiCOnz119KTlRU50HTwa4pvIgLphf9htTbPzHXS iEb8yINqMxmep8NRcAzwFREQP+Z4Tue1upt31Vx0RPkFZpUklLuuBSXsV0JA7+UM LSGyWhkzDdnfj6iPUHycGmFzRTzkbB7qfcMj7khCvuYtSNbTUdOgUq04ngZksrSJ UMhfgUNKXawULKvVe7572L/AQTmMXK8eaolb+eWtf1U2pFkZQR8GWoLmiFbKLks2 X2tRUF4U4cHEBzxXRzYrD1ArWLajqK6hQmauwgkCCSowvCHoD1dTv55GlrlEo4od MSB6YOVLl7HJuUw1GmwlKjA8XqStHq1Fi0urvlKCfHfK2Wk= =MP+m - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBXxE9l+NLKJtyKPYoAQi9zQ//Z2iQqm+eMPrvxTHSbOK1J2CGGto/qrBY n8CA0u49V8tV9PJGkLVKnD79FqGsP9fZ8I5ymWwP2BPePIGm7d09n8b9u+X6sLuh khn8mFy+JXLdbQs4T92jTkmKEffo+j38oSfOR06KkLg8LrT52IC2UNlsfPt21v9l IWYJtbYkOOCLRx3qiGljjzJNgxOBk+O0gDm40IkjpiLvLjnI/2wkcQ8k8CXoB5Ek yT5vCWd47CqxihK69CRfiivQSVwnTNKG3bhdoyJhLqfBM5nNuNYHTn7a/CW3rptu pbSwX+l8wXgBzm6fgo1tXyV1VlnH9vlrGccN0KnMF9jyWr/i17ktUrUDj7gTDsjZ QAmbCdN4Rac5VfU0PzLhGRhLBLGteZpGcZB/Cdigv9ir6NJlTcpQ2WQzMJN1zeVA 4bbTo83aBE5++m9VNPzDC8J9bXNDFWKFild7/jSh+1FSi1AQB4r6yEGawBKGHhFG sMroxt9hqDf4yP12pgU0aOpIJGJGaUiypzuyumEfm0LhqzIFD6pAHEePdmt40JfZ 9rgKlRyoW+FwcpoIq+HT7/OgD5wSA4yK57MobuESmynJUSeCMomGt3GmC4EME9aO Tg2qPskXsGRJY9tdJ6w7uT08byr3aRTA0vMS32sEB7f5WDDXmmy2YsuspiryOxjk jEpIIWpS1wc= =ShZt -----END PGP SIGNATURE-----