On Fri, Aug 11, 2017 at 3:03 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > On Mon, Aug 07, 2017 at 05:24:08PM -0700, Dan Williams wrote: >> Does sys_mmap() reject unknown flag values today? I'm either not >> looking in the right place or it's missing and we'll need some >> interface/mechanism to check if MAP_SYNC is honored. > > It doesn't seem to reject unknown flags. > > The lack of flags checking strikes back once more, sighṫ. How about MAP_SYNC == (MAP_SHARED|MAP_PRIVATE)? On older kernels that should get -EINVAL, and on new kernels it means SYNC+SHARED.