An issue was discovered in Xen through 4.14.x. A bounds check common to most operation time functions specific to FIFO event channels depends on the CPU observing consistent state. While the producer side uses appropriately ordered writes, the consumer side isnt protected against re-ordered reads, and may hence end up de-referencing a NULL pointer. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. Only Arm systems may be vulnerable. Whether a system is vulnerable depends on the specific CPU. x86 systems are not vulnerable.
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Xen | Xen | 4.4.0 (including) | 4.14.0 (including) |
| Xen | Ubuntu | bionic | * |
| Xen | Ubuntu | esm-apps/focal | * |
| Xen | Ubuntu | esm-infra/bionic | * |
| Xen | Ubuntu | esm-infra/xenial | * |
| Xen | Ubuntu | focal | * |
| Xen | Ubuntu | groovy | * |
| Xen | Ubuntu | hirsute | * |
| Xen | Ubuntu | impish | * |
| Xen | Ubuntu | trusty | * |
| Xen | Ubuntu | xenial | * |