drm/ttm: fix incrementing the page pointer for huge pages

stable inclusion
from linux-4.19.97
commit 8c2cdfb2c81bb533b9e6a3874ee5399102c4c580
CVE: CVE-2019-19927

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

commit 45339336 upstream.

When we increment the counter we need to increment the pointer as well.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Fixes: e16858a7e6e7 drm/ttm: fix start page for huge page check in ttm_put_pages()
Reviewed-by: NMichel Dänzer <michel.daenzer@amd.com>
Acked-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

@@ -733,7 +733,7 @@ static void ttm_put_pages(struct page **pages, unsigned npages, int flags,
 			if (!(flags & TTM_PAGE_FLAG_DMA32) &&
 			    (npages - i) >= HPAGE_PMD_NR) {
 				for (j = 1; j < HPAGE_PMD_NR; ++j)
-					if (p++ != pages[i + j])
+					if (++p != pages[i + j])
 					    break;
 
 				if (j == HPAGE_PMD_NR)
@@ -768,7 +768,7 @@ static void ttm_put_pages(struct page **pages, unsigned npages, int flags,
 				break;
 
 			for (j = 1; j < HPAGE_PMD_NR; ++j)
-				if (p++ != pages[i + j])
+				if (++p != pages[i + j])
 				    break;
 
 			if (j != HPAGE_PMD_NR)