userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas

[uclinux-h8/linux.git] / mm / userfaultfd.c

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 471b645..43cf314 100644 (file)
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -205,8 +205,9 @@ retry:
                if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
                        goto out_unlock;
                /*
-                * Only allow __mcopy_atomic_hugetlb on userfaultfd
-                * registered ranges.
+                * 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;
@@ -459,13 +460,9 @@ retry:
        if (!dst_vma)
                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;