CVE-2020-29571
Description
From CVE.org
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 isn't 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.
Statement
Red Hat Product Security has determined that this vulnerability does not affect any currently supported Red Hat product. This assessment may evolve based on further analysis and discovery. For more information about this vulnerability and the products it affects, please see the linked references.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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