On Tue, Apr 02, 2019 at 10:15:38AM -0600, Alex Williamson 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> Have you tested with GPU passthrough ? GPU have huge BAR from hundred of mega bytes to giga bytes (some driver resize them to cover the whole GPU memory). Driver need to map those to properly work. I am not sure what path is taken by mmap of mmio BAR by a guest on the host but i just thought i would point that out. Cheers, Jérôme
