Bugzilla – Bug 903967
VUL-0: CVE-2014-8594: XSA-109: xen: Insufficient restrictions on certain MMU update hypercalls
Last modified: 2016-11-22 17:18:49 UTC
*** EMBARGOED UNTIL 2014-11-18 12:00 UTC *** ISSUE DESCRIPTION ================= MMU update operations targeting page tables are intended to be used on PV guests only. The lack of a respective check made it possible for such operations to access certain function pointers which remain NULL when the target guest is using Hardware Assisted Paging (HAP). IMPACT ====== Malicious or buggy stub domain kernels or tool stacks otherwise living outside of Domain0 can mount a denial of service attack which, if successful, can affect the whole system. Only PV domains with privilege over other guests can exploit this vulnerability; and only when those other guests are HVM using HAP, or PVH. The vulnerability is therefore exposed to PV domains providing hardware emulation services to HVM guests. VULNERABLE SYSTEMS ================== Xen 4.0 and onward are vulnerable. Only x86 systems are vulnerable. ARM systems are not vulnerable. The vulnerability is only exposed to PV service domains for HVM or PVH guests which have privilege over the guest. In a usual configuration that means only device model emulators (qemu-dm). 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. The situation is more subtle 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). The same applies with a qemu-dm in a dom0 process subjected to some kind kernel-based process privilege limitation (eg the chroot technique as found in some versions of XCP/XenServer). In those latter situations this issue means that the extra isolation does not provide as good a defence (against denial of service) as intended. That is the essence of this vulnerability. However, the security 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 HVM or PVH 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. MITIGATION ========== Running only PV guests or HVM guests with shadow paging enabled will avoid this issue. In a radically disaggregated system, restricting HVM service domains to software images approved by the host administrator will avoid the vulnerability. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa109.patch xen-unstable, Xen 4.4.x, Xen 4.3.x xsa109-4.2.patch Xen 4.2.x $ sha256sum xsa109*.patch 759d1b8cb8c17e53d17ad045ab89c5aaf52cb85fd93eef07e7acbe230365c56d xsa109-4.2.patch 729b87c2b9979fbda47c96e934db6fcfaeb10e07b4cfd66bb1e9f746a908576b xsa109.patch
Created attachment 612447 [details] xen-unstable, Xen 4.4.x, Xen 4.3.x
Created attachment 612448 [details] Xen 4.2.x
bugbot adjusting priority
CVE got assigned: CVE-2014-8594
An update workflow for this issue was started. This issue was rated as moderate. Please submit fixed packages until 2014-11-27. When done, reassign the bug to security-team@suse.de. https://swamp.suse.de/webswamp/wf/59647
Xen has been submitted with the following MR/SR numbers: SLE12: MR#46616 SLE11-SP3: SR#46617 SLE11-SP2: SR#46618 SLE11-SP1: SR#46619 SLE11-SP1-Teradata: SR#46622
SUSE-SU-2014:1700-1: An update that solves 5 vulnerabilities and has 5 fixes is now available. Category: security (moderate) Bug References: 866902,882089,896023,901317,903850,903967,903970,905465,905467,906439 CVE References: CVE-2014-8594,CVE-2014-8595,CVE-2014-8866,CVE-2014-8867,CVE-2014-9030 Sources used: SUSE Linux Enterprise Software Development Kit 11 SP3 (src): xen-4.2.5_02-0.7.1 SUSE Linux Enterprise Server 11 SP3 (src): xen-4.2.5_02-0.7.1 SUSE Linux Enterprise Desktop 11 SP3 (src): xen-4.2.5_02-0.7.1
SUSE-SU-2014:1710-1: An update that solves 13 vulnerabilities and has two fixes is now available. Category: security (moderate) Bug References: 826717,867910,875668,880751,895798,895799,895802,897657,901317,903850,903967,903970,905465,905467,906439 CVE References: CVE-2013-3495,CVE-2014-2599,CVE-2014-3124,CVE-2014-4021,CVE-2014-7154,CVE-2014-7155,CVE-2014-7156,CVE-2014-7188,CVE-2014-8594,CVE-2014-8595,CVE-2014-8866,CVE-2014-8867,CVE-2014-9030 Sources used: SUSE Linux Enterprise Server 11 SP2 LTSS (src): xen-4.1.6_08-0.5.1
SUSE-SU-2014:1732-1: An update that fixes 9 vulnerabilities is now available. Category: security (moderate) Bug References: 826717,880751,895798,895799,895802,903967,903970,905467,906439 CVE References: CVE-2013-3495,CVE-2014-4021,CVE-2014-7154,CVE-2014-7155,CVE-2014-7156,CVE-2014-8594,CVE-2014-8595,CVE-2014-8867,CVE-2014-9030 Sources used: SUSE Linux Enterprise Server 11 SP1 LTSS (src): xen-4.0.3_21548_18-0.9.1
SUSE-SU-2015:0022-1: An update that solves 8 vulnerabilities and has 10 fixes is now available. Category: security (important) Bug References: 826717,866902,882089,889526,896023,897614,897906,898772,900292,901317,903357,903359,903850,903967,903970,905465,905467,906439 CVE References: CVE-2013-3495,CVE-2014-5146,CVE-2014-5149,CVE-2014-8594,CVE-2014-8595,CVE-2014-8866,CVE-2014-8867,CVE-2014-9030 Sources used: SUSE Linux Enterprise Software Development Kit 12 (src): xen-4.4.1_08-5.2 SUSE Linux Enterprise Server 12 (src): xen-4.4.1_08-5.2 SUSE Linux Enterprise Desktop 12 (src): xen-4.4.1_08-5.2
openSUSE-SU-2015:0226-1: An update that solves 11 vulnerabilities and has 5 fixes is now available. Category: security (important) Bug References: 826717,866902,882089,889526,900292,901317,903357,903359,903850,903967,903970,905465,905467,906439,906996,910681 CVE References: CVE-2013-3495,CVE-2014-5146,CVE-2014-5149,CVE-2014-8594,CVE-2014-8595,CVE-2014-8866,CVE-2014-8867,CVE-2014-9030,CVE-2014-9065,CVE-2014-9066,CVE-2015-0361 Sources used: openSUSE 13.1 (src): xen-4.3.3_04-34.1
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openSUSE-SU-2015:0256-1: An update that solves 11 vulnerabilities and has 9 fixes is now available. Category: security (important) Bug References: 826717,866902,882089,889526,896023,897906,898772,900292,901317,903357,903359,903850,903967,903970,904255,905465,905467,906439,906996,910681 CVE References: CVE-2013-3495,CVE-2014-5146,CVE-2014-5149,CVE-2014-8594,CVE-2014-8595,CVE-2014-8866,CVE-2014-8867,CVE-2014-9030,CVE-2014-9065,CVE-2014-9066,CVE-2015-0361 Sources used: openSUSE 13.2 (src): xen-4.4.1_08-9.1