From: Dan Williams dan.j.williams@intel.com Subject: mm: fail get_vaddr_frames() for filesystem-dax mappings

Until there is a solution to the dma-to-dax vs truncate problem it is not safe to allow V4L2, Exynos, and other frame vector users to create long standing / irrevocable memory registrations against filesytem-dax vmas.

[dan.j.williams@intel.com: add comment for vma_is_fsdax() check in get_vaddr_frames(), per Jan] Link: http://lkml.kernel.org/r/151197874035.26211.4061781453123083667.stgit@dwilli... Link: http://lkml.kernel.org/r/151068939985.7446.15684639617389154187.stgit@dwilli... Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Signed-off-by: Dan Williams dan.j.williams@intel.com Reviewed-by: Jan Kara jack@suse.cz Cc: Inki Dae inki.dae@samsung.com Cc: Seung-Woo Kim sw0312.kim@samsung.com Cc: Joonyoung Shim jy0922.shim@samsung.com Cc: Kyungmin Park kyungmin.park@samsung.com Cc: Mauro Carvalho Chehab mchehab@kernel.org Cc: Mel Gorman mgorman@suse.de Cc: Vlastimil Babka vbabka@suse.cz Cc: Christoph Hellwig hch@lst.de Cc: Doug Ledford dledford@redhat.com Cc: Hal Rosenstock hal.rosenstock@gmail.com Cc: Jason Gunthorpe jgg@mellanox.com Cc: Jeff Moyer jmoyer@redhat.com Cc: Ross Zwisler ross.zwisler@linux.intel.com Cc: Sean Hefty sean.hefty@intel.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/frame_vector.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)

diff -puN mm/frame_vector.c~mm-fail-get_vaddr_frames-for-filesystem-dax-mappings mm/frame_vector.c --- a/mm/frame_vector.c~mm-fail-get_vaddr_frames-for-filesystem-dax-mappings +++ a/mm/frame_vector.c @@ -53,6 +53,18 @@ int get_vaddr_frames(unsigned long start ret = -EFAULT; goto out; } + + /* + * While get_vaddr_frames() could be used for transient (kernel + * controlled lifetime) pinning of memory pages all current + * users establish long term (userspace controlled lifetime) + * page pinning. Treat get_vaddr_frames() like + * get_user_pages_longterm() and disallow it for filesystem-dax + * mappings. + */ + if (vma_is_fsdax(vma)) + return -EOPNOTSUPP; + if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) { vec->got_ref = true; vec->is_pfns = false; _