[v2.6] xen: multiple issues (CVE-2015-2751, CVE-2015-2756, CVE-2015-3340)
Xen Security Advisory 126 (CVE-2015-2756) - Unmediated PCI command
register access in qemu
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VULNERABLE SYSTEMS ==
Xen versions 3.3 and onwards are vulnerable due to supporting PCI
pass-through.
Only x86 systems are vulnerable. ARM systems are not vulnerable.
Only HVM guests with their device model run in Dom0 can take advantage
of this vulnerability.
Any domain which is given access to a non-SR-IOV virtual function PCI
Express device can take advantage of this vulnerability.
http://xenbits.xen.org/xsa/advisory-126.html
Xen Security Advisory 127 (CVE-2015-2751) - Certain domctl operations
may be abused to lock up the host
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VULNERABLE SYSTEMS ==
Xen versions 4.3 onwards are vulnerable. Xen versions 4.2 and earlier do
not have the described disaggregation functionality and hence are not
vulnerable.
http://xenbits.xen.org/xsa/advisory-127.html
Xen Security Advisory 132 (CVE-2015-3340) - Information leak through
XEN_DOMCTL_gettscinfo
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VULNERABLE SYSTEMS ==
Xen 4.0.x and later are vulnerable. Only x86 systems are vulnerable. ARM
systems are not vulnerable.
The vulnerability is only exposed to service domains with privilege over another guest. In a usual configuration that means only device model emulators (qemu-dm) when these are running in a separate domain.
In the case of HVM guests whose device model is running in an unrestricted dom0 process, qemu-dm already has the ability to cause problems for the whole system. So in that case the vulnerability is not applicable.
This vulnerability is applicable for an HVM guest with a stub qemu-dm. That is, where the device model runs in a separate domain (in the case of xl, as requested by “device_model_stubdomain_override=1” in the xl domain configuration file). In this case a guest which has already exploited another vulnerability, to gain control of the device model, would be able to exercise the information leak.
However, the security of a system with qemu-dm running in a stub domain is still better than with a qemu-dm running as an unrestricted dom0 process. Therefore users with these configurations should not switch to an unrestricted dom0 qemu-dm.
Finally, in a radically disaggregated system, where the service domain software (probably, the device model domain image in the HVM case) is not always supplied by the host administrator, a malicious service domain administrator can exercise this vulnerability.
http://xenbits.xen.org/xsa/advisory-132.html
(from redmine: issue id 4087, created on 2015-04-21, closed on 2017-09-05)
- Relations:
- parent #4086