Re: [PATCH v2 v4.14.y 0/3] vfio: Fix for CVE-2020-12888

Greg KH
2020-09-10T17:13:43Z

On Wed, Sep 09, 2020 at 12:24:23AM +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.
>
> Upstreamed patches link:
> https://lore.kernel.org/kvm/158871401328.15589.17598154478222071285.stgit@gimli.home
>
> Diff from v1:
> Fixed build break problem.
>
> [PATCH v2 v4.14.y 1/3]:
> Backporting of upsream commit 41311242221e:
> vfio/type1: Support faulting PFNMAP vmas
>
> [PATCH v2 v4.14.y 2/3]:
> Backporting of upsream commit 11c4cd07ba11:
> vfio-pci: Fault mmaps to enable vma tracking
>
> [PATCH v2 v4.14.y 3/3]:
> Backporting of upsream commit abafbc551fdd:
> vfio-pci: Invalidate mmaps and block MMIO access on disabled memory

This worked better, now all queued up, thanks!

greg k-h