On Sun, Sep 06, 2020 at 07:37:57PM +0530, Ajay Kaher wrote:
CVE-2020-12888 Kernel: vfio: access to disabled MMIO space of some devices may lead to DoS scenario
The VFIO modules allow users (guest VMs) to enable or disable access to the devices' MMIO memory address spaces. If a user attempts to access (read/write) the devices' MMIO address space when it is disabled, some h/w devices issue an interrupt to the CPU to indicate a fatal error condition, crashing the system. This flaw allows a guest user or process to crash the host system resulting in a denial of service.
Patch 1/ is to force the user fault if PFNMAP vma might be DMA mapped before user access.
Patch 2/ setup a vm_ops handler to support dynamic faulting instead of calling remap_pfn_range(). Also provides a list of vmas actively mapping the area which can later use to invalidate those mappings.
Patch 3/ block the user from accessing memory spaces which is disabled by using new vma list support to zap, or invalidate, those memory mappings in order to force them to be faulted back in on access.
I've queued this and the 4.19 backports, thanks!