CVE-2018-15468

An issue was discovered in Xen through 4.11.x. The DEBUGCTL MSR contains several debugging features, some of which virtualise cleanly, but some do not. In particular, Branch Trace Store is not virtualised by the processor, and software has to be careful to configure it suitably not to lock up the core. As a result, it must only be available to fully trusted guests. Unfortunately, in the case that vPMU is disabled, all value checking was skipped, allowing the guest to choose any MSR_DEBUGCTL setting it likes. A malicious or buggy guest administrator (on Intel x86 HVM or PVH) can lock up the entire host, causing a Denial of Service.

An issue was discovered in Xen through 4.11.x. The DEBUGCTL MSR contains several debugging features, some of which virtualise cleanly, but some do not. In particular, Branch Trace Store is not virtualised by the processor, and software has to be careful to configure it suitably not to lock up the core. As a result, it must only be available to fully trusted guests. Unfortunately, in the case that vPMU is disabled, all value checking was skipped, allowing the guest to choose any MSR_DEBUGCTL setting it likes. A malicious or buggy guest administrator (on Intel x86 HVM or PVH) can lock up the entire host, causing a Denial of Service.

These are all security issues fixed in the xen-4.15.1_01-1.2 package on the GA media of openSUSE Tumbleweed.

This update for xen fixes the following issues:

• CVE-2018-17963: qemu_deliver_packet_iov accepted packet sizes greater than INT_MAX, which allows attackers to cause a denial of service or possibly have unspecified other impact. (bsc#1111014)
• CVE-2018-15468: The DEBUGCTL MSR contains several debugging features, some of which virtualise cleanly, but some do not. In particular, Branch Trace Store is not virtualised by the processor, and software has to be careful to configure it suitably not to lock up the core. As a result, it must only be available to fully trusted guests. Unfortunately, in the case that vPMU is disabled, all value checking was skipped, allowing the guest to choose any MSR_DEBUGCTL setting it likes. A malicious or buggy guest administrator (on Intel x86 HVM or PVH) could have locked up the entire host, causing a Denial of Service. (XSA-269) (bsc#1103276)

Non security issues fixed:

• Kernel oops in fs/dcache.c called by d_materialise_unique() (bsc#1094508)

This update for xen fixes the following issues:

XEN was updated to the Xen 4.9.3 bug fix only release (bsc#1027519)

• CVE-2018-17963: qemu_deliver_packet_iov accepted packet sizes greater than INT_MAX, which allows attackers to cause a denial of service or possibly have unspecified other impact. (bsc#1111014)
• CVE-2018-15470: oxenstored might not have enforced the configured quota-maxentity. This allowed a malicious or buggy guest to write as many xenstore entries as it wishes, causing unbounded memory usage in oxenstored. This can lead to a system-wide DoS. (XSA-272) (bsc#1103279)
• CVE-2018-15469: ARM never properly implemented grant table v2, either in the hypervisor or in Linux. Unfortunately, an ARM guest can still request v2 grant tables; they will simply not be properly set up, resulting in subsequent grant-related hypercalls hitting BUG() checks. An unprivileged guest can cause a BUG() check in the hypervisor, resulting in a denial-of-service (crash). (XSA-268) (bsc#1103275) Note that SUSE does not ship ARM Xen, so we are not affected.
• CVE-2018-15468: The DEBUGCTL MSR contains several debugging features, some of which virtualise cleanly, but some do not. In particular, Branch Trace Store is not virtualised by the processor, and software has to be careful to configure it suitably not to lock up the core. As a result, it must only be available to fully trusted guests. Unfortunately, in the case that vPMU is disabled, all value checking was skipped, allowing the guest to choose any MSR_DEBUGCTL setting it likes. A malicious or buggy guest administrator (on Intel x86 HVM or PVH) can lock up the entire host, causing a Denial of Service. (XSA-269) (bsc#1103276)
• CVE-2018-3646: Systems with microprocessors utilizing speculative execution and address translations may have allowed unauthorized disclosure of information residing in the L1 data cache to an attacker with local user access with guest OS privilege via a terminal page fault and a side-channel analysis. (XSA-273) (bsc#1091107)

Non security issues fixed:

• The affinity reporting via 'xl vcpu-list' was broken (bsc#1106263)
• Kernel oops in fs/dcache.c called by d_materialise_unique() (bsc#1094508)

This update for xen fixes the following issues:

Update to Xen 4.10.2 bug fix release (bsc#1027519).

Security vulnerabilities fixed:

• CVE-2018-19961, CVE-2018-19962: Fixed an issue related to insufficient TLB flushing with AMD IOMMUs, which potentially allowed a guest to escalate its privileges, may cause a Denial of Service (DoS) affecting the entire host, or may be able to access data it is not supposed to access. (XSA-275) (bsc#1115040)
• CVE-2018-19965: Fixed an issue related to the INVPCID instruction in case non-canonical addresses are accessed, which may allow a guest to cause Xen to crash, resulting in a Denial of Service (DoS) affecting the entire host. (XSA-279) (bsc#1115045)
• CVE-2018-19966: Fixed an issue related to a previous fix for XSA-240, which conflicted with shadow paging and allowed a guest to cause Xen to crash, resulting in a Denial of Service (DoS). (XSA-280) (bsc#1115047)
• CVE-2018-18883: Fixed an issue related to inproper restriction of nested VT-x, which allowed a guest to cause Xen to crash, resulting in a Denial of Service (DoS). (XSA-278) (bsc#1114405)
• CVE-2018-15468: Fixed incorrect MSR_DEBUGCTL handling, which allowed guests to enable Branch Trace Store and may cause a Denial of Service (DoS) of the entire host. (XSA-269) (bsc#1103276)
• CVE-2018-15469: Fixed use of v2 grant tables on ARM, which were not properly implemented and may cause a Denial of Service (DoS). (XSA-268) (bsc#1103275)
• CVE-2018-15470: Fixed an issue in the logic in oxenstored for handling writes, which allowed a guest to write memory unbounded leading to system-wide Denial of Service (DoS). (XSA-272) (bsc#1103279)
• CVE-2018-3646: Mitigations for VMM aspects of L1 Terminal Fault (XSA-273) (bsc#1091107)

Other bugs fixed:

• Fixed an issue related to a domU hang on SLE12-SP3 HV (bsc#1108940)
• Fixed an issue with xpti=no-dom0 not working as expected (bsc#1105528)
• Fixed a kernel oops related to fs/dcache.c called by d_materialise_unique() (bsc#1094508)