Re: [PATCH v4.4,v4.9] vfio/type1: Limit DMA mappings per container

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, May 02, 2019 at 06:33:23AM -0700, Guenter Roeck wrote:
> From: Alex Williamson <alex.williamson@redhat.com>
> 
> commit 492855939bdb59c6f947b0b5b44af9ad82b7e38c upstream.
> 
> Memory backed DMA mappings are accounted against a user's locked
> memory limit, including multiple mappings of the same memory.  This
> accounting bounds the number of such mappings that a user can create.
> However, DMA mappings that are not backed by memory, such as DMA
> mappings of device MMIO via mmaps, do not make use of page pinning
> and therefore do not count against the user's locked memory limit.
> These mappings still consume memory, but the memory is not well
> associated to the process for the purpose of oom killing a task.
> 
> To add bounding on this use case, we introduce a limit to the total
> number of concurrent DMA mappings that a user is allowed to create.
> This limit is exposed as a tunable module option where the default
> value of 64K is expected to be well in excess of any reasonable use
> case (a large virtual machine configuration would typically only make
> use of tens of concurrent mappings).
> 
> This fixes CVE-2019-3882.
> 
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Tested-by: Eric Auger <eric.auger@redhat.com>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> [groeck: Adjust for missing upstream commit]
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)

Nice, thanks for the backport, now queued up!

greg k-h