Xen vulnerabilities

When switching from Grant Table v2 to v1 in Xen, code holding the grant table lock but temporarily dropping and re-acquiring it wrongly assumes that table properties won't change during the window without the lock. This leads to issues with status frames that disappear when switching from v2 to v1.

When switching from Grant Table v1 to v2 in Xen, code holding the grant table lock but temporarily dropping and re-acquiring it wrongly assumes that table properties won't change during the window without the lock. This leads to a reduction in the number of valid grant references.

A guest with Populated on Demand (PoD) enabled may attempt to reclaim pages that are not regular guest RAM. This can cause corruption of memory management state in Xen.

The EVTCHNOP_expand_array hypercall checks for FIFO event channels being enabled, but without holding the correct lock. It can race with EVTCHNOP_reset, resulting in dereferencing a NULL pointer.

The logic to handle periodic Viridian STIMERs performs a division with an unchecked user-controlled divisor value, that can be set to zero to cause a #DE fault.

Accesses to CMOS memory contents are done using an indirect IO port pair. Xen needs to cache the guest chosen index, and one of the usages of the index didn't take the necessary locking to avoid concurrent changes, allowing a guest to change the index after it being checked, causing an out-of-bound read access.

Accessing vNUMA configuration data of a guest is still possible when domain destruction has already started. The cleanup of that configuration information is not synchronized with its retrieval by a device model controlling the guest.

When grant-copy operations are processed, permission checks may be carried out on a page different from the one involved in the copy when the grant is already pinned, leading to inconsistency.

Platform-op operations use a system-wide lock, but the lock acquisition lacks fairness, and with XSM/Flask enabled, the lock is acquired before permission checks. This is the platform-op issue.

Sysctl operations use a system-wide lock, but the lock acquisition lacks fairness, and with XSM/Flask enabled, the lock is acquired before permission checks. This is the sysctl issue.

Addressing certain issues related to long-running operations has proven overly costly. Since alternatives (HVM/PVH: HAP, PV: shim) are commonly available, the decision was to deprecate the functionality, while still retaining it for use at own risk. Memory-wise small guests may still be okay to run.

Xenstore uses a new XEN_DOMCTL_get_domain_state to track domains. The bitmap management is tied to the binding of VIRQ_DOM_EXC. Unfortunately, an error path can tear down the bitmap even when it wasn't set up. Unprivileged domains can trigger that error path.

An issue was discovered in Xen through 4.9.x allowing PV guest OS users to cause a denial of service (host OS crash) or gain host OS privileges in shadow mode by mapping a certain auxiliary page.

An issue was discovered in Xen through 4.9.x allowing guest OS users to cause a denial of service (host OS crash) or gain host OS privileges by leveraging incorrect error handling for reference counting in shadow mode.

An issue was discovered in Xen through 4.9.x allowing guest OS users to cause a denial of service (host OS crash) or gain host OS privileges. The issue arises from an incorrect mask for reference-count overflow checking in shadow mode.

An issue was discovered in Xen through 4.9.x allowing HVM guest OS users to gain privileges on the host OS, obtain sensitive information, or cause a denial of service (BUG and host OS crash) by leveraging the mishandling of Populate on Demand (PoD) Physical-to-Machine (P2M) errors.

A parameter verification issue was discovered in Xen through 4.9.x. The function `alloc_heap_pages` allows callers to specify the first NUMA node for allocations, but it does not properly handle the case where `node >= MAX_NUMNODES`, leading to out-of-bounds access to an internal array.

Xen allows local OS guest users to cause a denial of service (crash) or possibly obtain sensitive information or gain privileges via vectors involving transitive grants.

The grant-table feature in Xen through 4.8.x mishandles MMIO region grant references, allowing guest OS users to cause a denial of service (loss of grant trackability).

The grant-table feature in Xen through 4.8.x has a race condition leading to a double free, allowing guest OS users to cause a denial of service (memory consumption) or possibly obtain sensitive information or gain privileges.

Xen through 4.6.x on 64-bit platforms mishandles a failsafe callback, which might allow PV guest OS users to execute arbitrary code on the host OS.

The ioport_read and ioport_write functions in Xen may allow local x86 HVM guest OS administrators to gain qemu process privileges via out-of-range ioport access.

Xen through 4.8.x allows local 64-bit x86 HVM guest OS users to gain privileges by leveraging mishandling of SYSCALL singlestep during emulation.

Xen, when used on a system providing PV backends, allows local guest OS administrators to cause a denial of service (host OS crash) or gain privileges by writing to memory shared between the frontend and backend, known as a double fetch vulnerability.

Xen 4.4.x running on ARM systems does not properly check write permissions on virtual addresses, allowing local guest administrators to gain privileges via unspecified vectors.

When oxenstored tears down a domain, node data is cleaned up but usage counts are leaked. When the domain ID is reused, the new domain can create fewer nodes before being deemed over quota.

The grant-table feature in Xen through 4.8.x mishandles a GNTMAP_device_map and GNTMAP_host_map mapping, which can lead to count mismanagement and memory corruption. Guest OS users can cause a denial of service or gain privileged host OS access.

The shadow-paging feature in Xen through 4.8.x mismanages page references, leading to a race condition. This allows guest OS users to obtain Xen privileges, known as XSA-219.