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: 530dd992 ("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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>