CVE-2021-20221 QEMU: aarch64: GIC: out-of-bound heap buffer access via an interrupt ID field

[P J P <ppandit () redhat com>]

  Hello,

An out-of-bounds heap buffer access issue was found in the ARM Generic 
Interrupt Controller emulator of QEMU on aarch64 platform. The issue occurs 
because while writing an interrupt ID to the controller memory area, it is not 
masked to be 4 bits wide. It may lead to the said issue while updating 
controller state fields and their subsequent processing. A privileged guest 
user may use this flaw to crash the QEMU process on the host resulting in DoS 
scenario.

It requires unusual kernel start-up with 'kernel-irqchip=off'.

It does not affect default configuration ie. kernel-irqchip=on.

Upstream patch:
---------------
  -> https://gitlab.com/qemu-project/qemu/-/commit/edfe2eb4360cde4ed5d95bda7777edcb3510f76a

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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