The PV pagetable code in arch/x86/mm.c in Xen 4.7.x and earlier allows local 32-bit PV guest OS administrators to gain host OS privileges by leveraging fast-paths for updating pagetable entries.
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.
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.
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.
The dommuupdate function in arch/x86/mm.c in Xen 3.2.x through 4.4.x does not properly manage page references, which allows remote domains to cause a denial of service by leveraging control over an HVM guest and a crafted MMUMACHPHYSUPDATE.
The XENMEMexchange handler in Xen 4.2 and earlier does not properly check the memory address, which allows local PV guest OS administrators to cause a denial of service (crash) or possibly gain privileges via unspecified vectors that overwrite memory in the hypervisor reserved range.
The paginginvlpg function in include/asm-x86/paging.h in Xen 3.3.x through 4.6.x, when using shadow mode paging or nested virtualization is enabled, allows local HVM guest users to cause a denial of service (host crash) via a non-canonical guest address in an INVVPID instruction, which triggers a hypervisor bug check.
The x86emulate function in arch/x86/x86emulate/x86emulate.c in Xen 4.4.x and earlier does not properly check supervisor mode permissions, which allows local HVM users to cause a denial of service (guest crash) or gain guest kernel mode privileges via vectors involving an (1) HLT, (2) LGDT, (3) LIDT, or (4) LMSW instruction.
The vmxsetucmode function in Xen 3.3 through 4.3, when disabling caches, allows local HVM guests with access to memory mapped I/O regions to cause a denial of service (CPU consumption and possibly hypervisor or guest kernel panic) via a crafted GFN range.
Xen, possibly before 4.0.2, allows local 64-bit PV guests to cause a denial of service (host crash) by specifying user mode execution without user-mode pagetables.
Memory leak in Xen 3.3 through 4.8.x allows guest OS users to cause a denial of service (ARM or x86 AMD host OS memory consumption) by continually rebooting, because certain cleanup is skipped if no pass-through device was ever assigned, aka XSA-207.
The XENDOMCTLgetmemlist hypercall in Xen 3.4.x through 4.3.x (possibly 4.3.1) does not always obtain the pagealloclock and mmrwlock in the same order, which allows local guest administrators to cause a denial of service (host deadlock).
Xen 3.0.3 through 4.1.x (possibly 4.1.6.1), 4.2.x (possibly 4.2.3), and 4.3.x (possibly 4.3.1) does not properly prevent access to hypercalls, which allows local guest users to gain privileges via a crafted application running in ring 1 or 2.
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.
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.
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 to cause a denial of service (host interrupt handling confusion) via vectors related to qemu and accessing spanning multiple fields.
The p2mpodemergencysweep 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.
ISSUE DESCRIPTION =================
Guests are currently permitted to modify all of the (writable) bits in the PCI command register of devices passed through to them. This in particular allows them to disable memory and I/O decoding on the device unless the device is an SR-IOV virtual function, in which case subsequent accesses to the respective MMIO or I/O port ranges would - - on PCI Express devices - lead to Unsupported Request responses. The treatmeant of such errors is platform specific.
IMPACT ======
In the event that the platform surfaces aforementioned UR responses as Non-Maskable Interrupts, and either the OS is configured to treat NMIs as fatal or (e.g. via ACPI's APEI) the platform tells the OS to treat these errors as fatal, the host would crash, leading to a Denial of Service.
VULNERABLE SYSTEMS ==================
Xen versions 3.3 and onwards are vulnerable due to supporting PCI pass-through. Upstream Linux versions 3.1 and onwards are vulnerable due to supporting PCI backend functionality. Other Linux versions as well as other OS versions may be vulnerable too.
Any domain which is given access to a non-SR-IOV virtual function PCI Express device can take advantage of this vulnerability.
MITIGATION ==========
This issue can be avoided by not assigning PCI Express devices other than SR-IOV virtual functions to untrusted guests.
RESOLUTION ==========
Applying the attached patch resolves this issue for upstream Linux.
xsa120.patch Linux 3.19
$ sha256sum xsa120.patch 5167215293d4a8a05f090fca5b20eb5878213a0158a0e7a12c245553db81a855 xsa120.patch
The guestphysmapmarkpopulateondemand function in Xen 4.2 and earlier does not properly unlock the subject GFNs when checking if they are in use, which allows local guest HVM administrators to cause a denial of service (hang) via unspecified vectors.
The (1) XENMEMdecreasereservation, (2) XENMEMpopulatephysmap, and (3) XENMEMexchange hypercalls in Xen 4.2 and earlier allow local guest administrators to cause a denial of service (long loop and hang) via a crafted extentorder value.
Multiple HVM control operations in Xen 3.4 through 4.2 allow local HVM guest OS administrators to cause a denial of service (physical CPU consumption) via a large input.
Stack-based buffer overflow in the dirty video RAM tracking functionality in Xen 3.4 through 4.1 allows local HVM guest OS administrators to cause a denial of service (crash) via a large bitmap image.
The Intel VT-d Interrupt Remapping engine in Xen 3.3.x through 4.3.x allows local guests to cause a denial of service (kernel panic) via a malformed Message Signaled Interrupt (MSI) from a PCI device that is bus mastering capable that triggers a System Error Reporting (SERR) Non-Maskable Interrupt (NMI).
The compatibility mode hypercall argument translation in Xen 3.3.x through 4.4.x, when running on a 64-bit hypervisor, allows local 32-bit HVM guests to cause a denial of service (host crash) via vectors involving altering the high halves of registers while in 64-bit mode.
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.
The memoryexchange 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.
Xen 4.2.x, 4.1.x, and earlier, when the hypervisor is running "under memory pressure" and the Xen Security Module (XSM) is enabled, uses the wrong ordering of operations when extending the per-domain event channel tracking table, which causes a use-after-free and allows local guest kernels to inject arbitrary events and gain privileges via unspecified vectors.
Last updated 24 July 2024
Xen 3.4 through 4.2, and possibly earlier versions, does not properly synchronize the p2m and m2p tables when the setp2mentry function fails, which allows local HVM guest OS administrators to cause a denial of service (memory consumption and assertion failure), aka "Memory mapping failure DoS vulnerability."
The fbld instruction emulation in Xen 3.3.x through 4.3.x does not use the correct variable for the source effective address, which allows local HVM guests to obtain hypervisor stack information by reading the values used by the instruction.