diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9b36cc57329e..ade072a6fd24 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1197,6 +1197,10 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
  * followed by taking the mmap_sem for writing before modifying the
  * vmas or anything the coredump pretends not to change from under it.
  *
+ * It also has to be called when mmgrab() is used in the context of
+ * the process, but then the mm_count refcount is transferred outside
+ * the context of the process to run down_write() on that pinned mm.
+ *
  * NOTE: find_extend_vma() called from GUP context is the only place
  * that can modify the "mm" (notably the vm_start/end) under mmap_sem
  * for reading and outside the context of the process, so it is also
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e0cfc3a54b6a..8217ee5d66ef 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1004,6 +1004,9 @@ static void collapse_huge_page(struct mm_struct *mm,
 	 * handled by the anon_vma lock + PG_lock.
 	 */
 	down_write(&mm->mmap_sem);
+	result = SCAN_ANY_PROCESS;
+	if (!mmget_still_valid(mm))
+		goto out;
 	result = hugepage_vma_revalidate(mm, address, &vma);
 	if (result)
 		goto out;