diff options
| -rw-r--r-- | mm/userfaultfd.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 46c8949e5f8f..471b6457f95f 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -380,7 +380,17 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, { ssize_t err; - if (vma_is_anonymous(dst_vma)) { + /* + * The normal page fault path for a shmem will invoke the + * fault, fill the hole in the file and COW it right away. The + * result generates plain anonymous memory. So when we are + * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll + * generate anonymous memory directly without actually filling + * the hole. For the MAP_PRIVATE case the robustness check + * only happens in the pagetable (to verify it's still none) + * and not in the radix tree. + */ + if (!(dst_vma->vm_flags & VM_SHARED)) { if (!zeropage) err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, src_addr, page); @@ -489,7 +499,8 @@ retry: * dst_vma. */ err = -ENOMEM; - if (vma_is_anonymous(dst_vma) && unlikely(anon_vma_prepare(dst_vma))) + if (!(dst_vma->vm_flags & VM_SHARED) && + unlikely(anon_vma_prepare(dst_vma))) goto out_unlock; while (src_addr < src_start + len) { |