pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
{
	struct vm_area_struct *vma = find_vma(mm, addr);
	struct address_space *mapping = vma->vm_file->f_mapping;
	pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
			vma->vm_pgoff;
	struct vm_area_struct *svma;
	unsigned long saddr;
	pte_t *spte = NULL;
	pte_t *pte;
	spinlock_t *ptl;

	if (!vma_shareable(vma, addr))
		return (pte_t *)pmd_alloc(mm, pud, addr);

	i_mmap_lock_write(mapping);
	vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
		if (svma == vma)
			continue;

		saddr = page_table_shareable(svma, vma, addr, idx);
		if (saddr) {
			spte = huge_pte_offset(svma->vm_mm, saddr,
					       vma_mmu_pagesize(svma));
			if (spte) {
				get_page(virt_to_page(spte));
				break;
			}
		}
	}

	if (!spte)
		goto out;

	ptl = huge_pte_lock(hstate_vma(vma), mm, spte);
	if (pud_none(*pud)) {
		pud_populate(mm, pud,
				(pmd_t *)((unsigned long)spte & PAGE_MASK));
		mm_inc_nr_pmds(mm);
	} else {
		put_page(virt_to_page(spte));
	}
	spin_unlock(ptl);
out:
	pte = (pte_t *)pmd_alloc(mm, pud, addr);
	i_mmap_unlock_write(mapping);
	return pte;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.