drm/ttm: fix start page for huge page check in ttm_put_pages()

stable inclusion
from linux-4.19.97
commit 83a88fb92950ef34b9924c39ff7554ae92c9af69
CVE: CVE-2019-19927

--------------------------------

commit ac1e516d upstream.

The first page entry is always the same with itself.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NMichel Dänzer <michel.daenzer@amd.com>
Reviewed-by: NJunwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: NHuang Rui <ray.huang@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: Zubin Mithra <zsm@chromium.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/gpu/drm/ttm/ttm_page_alloc.c

@@ -732,7 +732,7 @@ static void ttm_put_pages(struct page **pages, unsigned npages, int flags,
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 			if (!(flags & TTM_PAGE_FLAG_DMA32) &&
 			    (npages - i) >= HPAGE_PMD_NR) {
-				for (j = 0; j < HPAGE_PMD_NR; ++j)
+				for (j = 1; j < HPAGE_PMD_NR; ++j)
 					if (p++ != pages[i + j])
 					    break;
 
@@ -767,7 +767,7 @@ static void ttm_put_pages(struct page **pages, unsigned npages, int flags,
 			if (!p)
 				break;
 
-			for (j = 0; j < HPAGE_PMD_NR; ++j)
+			for (j = 1; j < HPAGE_PMD_NR; ++j)
 				if (p++ != pages[i + j])
 				    break;