On 10/9/26 20:04, Lorenzo Stoakes (ARM) wrote: > Rather than directly checking VMA flags, use the newly introduced > vma_is_mm_managed() and vma_is_mm_backed() helpers in userfaultfd > when assessing VMA suitability for userfaultfd and UFFDIO_MOVE. > > Update vma_move_compatible() so it's expressed in terms of VMA > characteristics rather than arbitrary flags. > > Additionally, update the use of the deprecated VMA flag API when checking > VMA_SHADOW_STACK_BIT. > > A VMA_IO_BIT check is no longer required but that is fine as a hard > invariant has been established that mm-managed mappings may not set > VMA_IO_BIT so the check is now redundant. > > Acked-by: Zi Yan <[email protected]> > Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]> > --- > mm/userfaultfd.c | 19 +++++++++++++------ > 1 file changed, 13 insertions(+), 6 deletions(-) > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index 949017e60608..f33b04700838 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -1754,10 +1754,16 @@ static inline bool move_splits_huge_pmd(unsigned long > dst_addr, > } > #endif > > -static inline bool vma_move_compatible(struct vm_area_struct *vma) > +static inline bool vma_move_compatible(const struct vm_area_struct *vma) > { > - return !(vma->vm_flags & (VM_PFNMAP | VM_IO | VM_HUGETLB | > - VM_MIXEDMAP | VM_SHADOW_STACK)); > + /* uffd is generally incompatible with mappings not managed by core mm. > */ > + if (!vma_is_mm_managed(vma)) > + return false; > + /* The shadow stack should not be written to by userspace. */ > + if (vma_test_single_mask(vma, VMA_SHADOW_STACK)) > + return false; > + /* hugetlb mappings cannot be safely moved. */ > + return !vma_is_hugetlb(vma); > } > > static int validate_move_areas(struct userfaultfd_ctx *ctx, > @@ -2146,10 +2152,11 @@ static bool vma_can_userfault(struct vm_area_struct > *vma, vm_flags_t vm_flags, > { > const struct vm_uffd_ops *ops = vma_uffd_ops(vma); > > - if (vma->vm_flags & (VM_DROPPABLE | VM_SHADOW_STACK)) > + /* Only mm-backed memory can have its faults handled by userspace. */ > + if (!vma_is_mm_backed(vma)) > return false;
Again, for both I would prefer keeping the droppable check separate. Acked-by: David Hildenbrand (Arm) <[email protected]> -- Cheers, David
