mm: use aligned address in copy_user_gigantic_page()

In current kernel, hugetlb_wp() calls copy_user_large_folio() with the
fault address.  Where the fault address may be not aligned with the huge
page size.  Then, copy_user_large_folio() may call
copy_user_gigantic_page() with the address, while
copy_user_gigantic_page() requires the address to be huge page size
aligned.  So, this may cause memory corruption or information leak,
addtional, use more obvious naming 'addr_hint' instead of 'addr' for
copy_user_gigantic_page().

Link: https://lkml.kernel.org/r/20241028145656.932941-2-wangkefeng.wang@huawei.com
Fixes: 530dd99 ("mm: memory: improve copy_user_large_folio()")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/hugetlb.c

@@ -5338,7 +5338,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 					break;
 				}
 				ret = copy_user_large_folio(new_folio, pte_folio,
-						ALIGN_DOWN(addr, sz), dst_vma);
+							    addr, dst_vma);
 				folio_put(pte_folio);
 				if (ret) {
 					folio_put(new_folio);
@@ -6641,8 +6641,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
 			*foliop = NULL;
 			goto out;
 		}
-		ret = copy_user_large_folio(folio, *foliop,
-					    ALIGN_DOWN(dst_addr, size), dst_vma);
+		ret = copy_user_large_folio(folio, *foliop, dst_addr, dst_vma);
 		folio_put(*foliop);
 		*foliop = NULL;
 		if (ret) {

mm/memory.c

@@ -6852,13 +6852,14 @@ void folio_zero_user(struct folio *folio, unsigned long addr_hint)
 }
 
 static int copy_user_gigantic_page(struct folio *dst, struct folio *src,
-				   unsigned long addr,
+				   unsigned long addr_hint,
 				   struct vm_area_struct *vma,
 				   unsigned int nr_pages)
 {
-	int i;
+	unsigned long addr = ALIGN_DOWN(addr_hint, folio_size(dst));
 	struct page *dst_page;
 	struct page *src_page;
+	int i;
 
 	for (i = 0; i < nr_pages; i++) {
 		dst_page = folio_page(dst, i);