From aaf863165e0920abe6c98026b131f9cca6ac9a0c Mon Sep 17 00:00:00 2001 From: Joel Fernandes Date: Fri, 15 Feb 2019 16:48:07 -0500 Subject: BACKPORT: userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas commit 29ec90660d68bbdd69507c1c8b4e33aa299278b1 upstream. After the VMA to register the uffd onto is found, check that it has VM_MAYWRITE set before allowing registration. This way we inherit all common code checks before allowing to fill file holes in shmem and hugetlbfs with UFFDIO_COPY. The userfaultfd memory model is not applicable for readonly files unless it's a MAP_PRIVATE. Change-Id: I55976c6eda20d68bdb8708d3b244731e3e4ce55c Link: http://lkml.kernel.org/r/20181126173452.26955-4-aarcange@redhat.com Fixes: ff62a3421044 ("hugetlb: implement memfd sealing") Signed-off-by: Andrea Arcangeli Reviewed-by: Mike Rapoport Reviewed-by: Hugh Dickins Reported-by: Jann Horn Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support") Cc: Cc: "Dr. David Alan Gilbert" Cc: Mike Kravetz Cc: Peter Xu Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman Signed-off-by: Joel Fernandes --- mm/userfaultfd.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) (limited to 'mm') diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 77fee9325a57..497248b93a4c 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -182,13 +182,9 @@ retry: goto out_unlock; /* - * Be strict and only allow __mcopy_atomic on userfaultfd - * registered ranges to prevent userland errors going - * unnoticed. As far as the VM consistency is concerned, it - * would be perfectly safe to remove this check, but there's - * no useful usage for __mcopy_atomic ouside of userfaultfd - * registered ranges. This is after all why these are ioctls - * belonging to the userfaultfd and not syscalls. + * Check the vma is registered in uffd, this is required to + * enforce the VM_MAYWRITE check done at uffd registration + * time. */ if (!dst_vma->vm_userfaultfd_ctx.ctx) goto out_unlock; -- cgit v1.2.3