MGASA-2016-0098

This xen update is based on upstream 4.5.2 maintenance release, and fixes the following security issues:

The vgicv2to_sgi function in arch/arm/vgic-v2.c in Xen 4.5.x, when running on ARM hardware with general interrupt controller (GIC) version 2, allows local guest users to cause a denial of service (host crash) by writing an invalid value to the GICD.SGIR register (CVE-2015-0268).

The ARM GIC distributor virtualization in Xen 4.4.x and 4.5.x allows local guests to cause a denial of service by causing a large number messages to be logged (CVE-2015-1563).

The emulation routines for unspecified X86 devices in Xen 3.2.x through 4.5.x does not properly initialize data, which allow local HVM guest users to obtain sensitive information via vectors involving an unsupported access size (CVE-2015-2044).

The HYPERVISORxenversion hypercall in Xen 3.2.x through 4.5.x does not properly initialize data structures, which allows local guest users to obtain sensitive information via unspecified vectors (CVE-2015-2045).

Xen 3.3.x through 4.5.x and the Linux kernel through 3.19.1 do not properly restrict access to PCI command registers, which might allow local guest users to cause a denial of service (non-maskable interrupt and host crash) by disabling the (1) memory or (2) I/O decoding for a PCI Express device and then accessing the device, which triggers an Unsupported Request (UR) response (CVE-2015-2150).

The x86 emulator in Xen 3.2.x through 4.5.x does not properly ignore segment overrides for instructions with register operands, which allows local guest users to obtain sensitive information, cause a denial of service (memory corruption), or possibly execute arbitrary code via unspecified vectors (CVE-2015-2151).

Xen 4.5.x and earlier enables certain default backends when emulating a VGA device for an x86 HVM guest qemu even when the configuration disables them, which allows local guest users to obtain access to the VGA console by (1) setting the DISPLAY environment variable, when compiled with SDL support, or connecting to the VNC server on (2) ::1 or (3) 127.0.0.1, when not compiled with SDL support (CVE-2015-2152).

Xen 4.3.x, 4.4.x, and 4.5.x, when using toolstack disaggregation, allows remote domains with partial management control to cause a denial of service (host lock) via unspecified domctl operations (CVE-2015-2751).

The XENDOMCTLmemory_mapping hypercall in Xen 3.2.x through 4.5.x, when using a PCI passthrough device, is not preemptable, which allows local x86 HVM domain users to cause a denial of service (host CPU consumption) via a crafted request to the device model (qemu-dm) (CVE-2015-2752).

QEMU, as used in Xen 3.3.x through 4.5.x, does not properly restrict access to PCI command registers, which might allow local HVM guest users to cause a denial of service (non-maskable interrupt and host crash) by disabling the (1) memory or (2) I/O decoding for a PCI Express device and then accessing the device, which triggers an Unsupported Request (UR) response (CVE-2015-2756).

Heap-based buffer overflow in the PCNET controller in QEMU allows remote attackers to execute arbitrary code by sending a packet with TXSTATUSSTARTPACKET set and then a crafted packet with TXSTATUSDEVICEOWNS set (CVE-2015-3209).

Stack-based buffer overflow in the xl command line utility in Xen 4.1.x through 4.5.x allows local guest administrators to gain privileges via a long configuration argument (CVE-2015-3259).

Xen 4.2.x through 4.5.x does not initialize certain fields, which allows certain remote service domains to obtain sensitive information from memory via a (1) XENDOMCTLgettscinfo or (2) XENSYSCTLgetdomaininfolist request (CVE-2015-3340).

The Floppy Disk Controller (FDC) in QEMU, as used in Xen 4.5.x and earlier and KVM, allows local guest users to cause a denial of service (out-of-bounds write and guest crash) or possibly execute arbitrary code via the (1) FDCMDREADID, (2) FDCMDDRIVESPECIFICATION_COMMAND, or other unspecified commands, aka VENOM (CVE-2015-3456).

Xen 3.3.x through 4.5.x does not properly restrict write access to the host MSI message data field, which allows local x86 HVM guest administrators cause a denial of service (host interrupt handling confusion) via vectors related to qemu and accessing spanning multiple fields (CVE-2015-4103).

Xen 3.3.x through 4.5.x does not properly restrict access to PCI MSI mask bits, which allows local x86 HVM guest users to cause a denial of service (unexpected interrupt and host crash) via unspecified vectors (CVE-2015-4104).

Xen 3.3.x through 4.5.x enables logging for PCI MSI-X pass-through error messages, which allows local x86 HVM guests to cause a denial of service (host disk consumption) via certain invalid operations (CVE-2015-4105).

QEMU does not properly restrict write access to the PCI config space for certain PCI pass-through devices, which mighy allow local x86 HVM guests to gain privileges, cause a denial of service (host crash), obtain sensitive information, or possibly have other unspecified impact via unknown vectors (CVE-2015-4106).

GNTTABOPswapgrantref in Xen 4.2 through 4.5 does not check the grant table operation version, which allows local guest domains to cause a denial of service (NULL pointer dereference) via a hypercall without a GNTTABOPsetuptable or GNTTABOPset_version (CVE-2015-4163).

The compatiret function in Xen 3.1 through 4.5 iterates the wrong way through a loop, which allows local 32-bit PV guest administrators to cause a denial of service (large loop and system hang) via a hypercalliret call with EFLAGS.VM set (CVE-2015-4164).

Heap-based buffer overflow in the IDE subsystem in QEMU, as used in Xen 4.5.x and earlier, when the container has a CDROM drive enabled, allows local guest users to execute arbitrary code on the host via unspecified ATAPI commands (CVE-2015-5154).

The C+ mode offload emulation in the RTL8139 network card device model in QEMU, as used in Xen 4.5.x and earlier, allows remote attackers to read process heap memory via unspecified vectors (CVE-2015-5165).

Use-after-free vulnerability in QEMU in Xen 4.5.x and earlier does not completely unplug emulated block devices, which allows local HVM guest users to gain privileges by unplugging a block device twice (CVE-2015-5166).

A guest to host DoS issue was found affecting various hypervisors. In that, a guest can DoS the host by triggering an infinite stream of "alignment check" (#AC) exceptions. This causes the microcode to enter an infinite loop where the core never receives another interrupt. The host kernel panics due to this effect (CVE-2015-5307).

The xenmemaddtophysmapone function in arch/arm/mm.c in Xen 4.5.x, 4.4.x, and earlier does not limit the number of printk console messages when reporting a failure to retrieve a reference on a foreign page, which allows remote domains to cause a denial of service by leveraging permissions to map the memory of a foreign guest (CVE-2015-6654).

libxl in Xen 4.1.x through 4.6.x does not properly handle the readonly flag on disks when using the qemu-xen device model, which allows local guest users to write to a read-only disk image (CVE-2015-7311).

A heap-based buffer overflow flaw was discovered in the way QEMU's AMD PC-Net II Ethernet Controller emulation received certain packets in loopback mode. A privileged user (with the CAPSYSRAWIO capability) inside a guest could use this flaw to crash the host QEMU process (resulting in denial of service) or, potentially, execute arbitrary code with privileges of the host QEMU process (CVE-2015-7504).

Multicall support for arm in xen 4.4.x and later was not correctly set up with correct functionality and therefore exposed to guests a code path which crashes the host. Any guest can issue a preemptable hypercall via the multicall interface to exploit this vulnerability (CVE-2015-7812).

Xen 4.4.x, 4.5.x, and 4.6.x does not limit the number of printk console messages when reporting unimplemented hypercalls, which allows local guests to cause a denial of service via a sequence of (1) HYPERVISORphysdevop hypercalls, which are not properly handled in the dophysdevop function in arch/arm/physdev.c, or (2) HYPERVISORhvmop hypercalls, which are not properly handled in the dohvmop function in arch/arm/hvm.c (CVE-2015-7813).

Race condition in the relinquishmemory function in arch/arm/domain.c in Xen 4.6.x and earlier allows local domains with partial management control to cause a denial of service (host crash) via vectors involving the destruction of a domain and using XENMEMdecrease_reservation to reduce the memory of the domain (CVE-2015-7814).

The modl2entry function in arch/x86/mm.c in Xen 3.4 through 4.6.x does not properly validate level 2 page table entries, which allows local PV guest administrators to gain privileges via a crafted superpage mapping (CVE-2015-7835).

Multiple memory leaks in Xen 4.0 through 4.6.x allow local guest administrators or domains with certain permission to cause a denial of service (memory consumption) via a large number of "teardowns" of domains with the vcpu pointer array allocated using the (1) XENDOMCTLmaxvcpus hypercall or the xenoprofile state vcpu pointer array allocated using the (2) XENOPROFgetbuffer or (3) XENOPROFset_passive hypercall (CVE-2015-7969).

The p2mpodemergency_sweep function in arch/x86/mm/p2m-pod.c in Xen 3.4.x, 3.5.x, and 3.6.x is not preemptible, which allows local x86 HVM guest administrators to cause a denial of service (CPU consumption and possibly reboot) via crafted memory contents that triggers a "time-consuming linear scan," related to Populate-on-Demand (CVE-2015-7970).

Xen 3.2.x through 4.6.x does not limit the number of printk console messages when logging certain pmu and profiling hypercalls, which allows local guests to cause a denial of service via a sequence of crafted (1) HYPERCALLxenoprofop hypercalls, which are not properly handled in the doxenoprofop function in common/xenoprof.c, or (2) HYPERVISORxenpmuop hypercalls, which are not properly handled in the doxenpmuop function in arch/x86/cpu/vpmu.c (CVE-2015-7971).

The (1) libxlsetmemorytarget function in tools/libxl/libxl.c and (2) libxlbuildpost function in tools/libxl/libxl_dom.c in Xen 3.4.x through 4.6.x do not properly calculate the balloon size when using the populate-on-demand (PoD) system, which allows local HVM guest users to cause a denial of service (guest crash) via unspecified vectors related to "heavy memory pressure." (CVE-2015-7972)

A guest to host DoS issue was found affecting various hypervisors. In that, a guest can DoS the host by triggering an infinite stream of "debug check" (#DB) exceptions. This causes the microcode to enter an infinite loop where the core never receives another interrupt. The host kernel panics due to this effect (CVE-2015-8104).

Xen 4.6.x and earlier does not properly enforce limits on page order inputs for the (1) XENMEMincreasereservation, (2) XENMEMpopulatephysmap, (3) XENMEMexchange, and possibly other HYPERVISORmemory_op suboperations, which allows ARM guest OS administrators to cause a denial of service (CPU consumption, guest reboot, or watchdog timeout and host reboot) and possibly have unspecified other impact via unknown vectors (CVE-2015-8338).

The memory_exchange function in common/memory.c in Xen 3.2.x through 4.6.x does not properly hand back pages to a domain, which might allow guest OS administrators to cause a denial of service (host crash) via unspecified vectors related to domain teardown (CVE-2015-8339).

The memoryexchange function in common/memory.c in Xen 3.2.x through 4.6.x does not properly release locks, which might allow guest OS administrators to cause a denial of service (deadlock or host crash) via unspecified vectors, related to XENMEMexchange error handling (CVE-2015-8340).

Felix Wilhelm discovered a race condition in the Xen paravirtualized drivers which can cause double fetch vulnerabilities. An attacker in the paravirtualized guest could exploit this flaw to cause a denial of service (crash the host) or potentially execute arbitrary code on the host (CVE-2015-8550).

Information leak in legacy x86 FPU/XMM initialization (CVE-2015-8555).

The PV superpage functionality lacks certain validity checks on data being passed to the hypervisor by guests. This is the case for the page identifier (MFN) passed to MMUEXTMARKSUPER and MMUEXTUNMARKSUPER sub-ops of the HYPERVISORmmuextop hypercall as well as for various forms of page table updates. Use of the feature, which is disabled by default, may have unknown effects, ranging from information leaks through Denial of Service to privilege escalation. (CVE-2016-1570)

While INVLPG does not cause a General Protection Fault when used on a non-canonical address, INVVPID in its "individual address" variant, which is used to back the intercepted INVLPG in certain cases, fails in such cases. Failure of INVVPID results in a hypervisor bug check. A malicious guest can crash the host, leading to a Denial of Service. (CVE-2016-1571)

Xen 4.6.x and earlier allows local guest administrators to cause a denial of service (host reboot) via vectors related to multiple mappings of MMIO pages with different cachability settings (CVE-2016-2270).

VMX in Xen 4.6.x and earlier, when using an Intel or Cyrix CPU, allows local HVM guest users to cause a denial of service (guest crash) via vectors related to a non-canonical RIP (CVE-2016-2271).

For other fixes in this update, see the referenced changelogs.