On Tue, 02 Apr 2019 10:15:38 -0600 Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > 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. > > Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > --- > > v2: Remove unnecessary atomic, all runtime access occurs while > holding vfio_iommu.lock. Change to unsigned int since we're > no longer bound by the atomic_t. > > drivers/vfio/vfio_iommu_type1.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) Non-atomic seems fine. Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
