drm/ttm: fix out-of-bounds read in ttm_put_pages() v2

When ttm_put_pages() tries to figure out whether it's dealing with
transparent hugepages, it just reads past the bounds of the pages array
without a check.

v2: simplify the test if enough pages are left in the array (Christian).

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Fixes: 5c42c64f7d54 ("drm/ttm: fix the fix for huge compound pages")
Cc: stable@vger.kernel.org
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
index f841accc2c00..f77c81db161b 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
@@ -730,7 +730,8 @@ static void ttm_put_pages(struct page **pages, unsigned npages, int flags,
                         }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-                        if (!(flags & TTM_PAGE_FLAG_DMA32)) {
+                        if (!(flags & TTM_PAGE_FLAG_DMA32) &&
+                            (npages - i) >= HPAGE_PMD_NR) {
                                 for (j = 0; j < HPAGE_PMD_NR; ++j)
                                         if (p++ != pages[i + j])
                                             break;
@@ -759,7 +760,7 @@ static void ttm_put_pages(struct page **pages, unsigned npages, int flags,
                 unsigned max_size, n2free;
 
                 spin_lock_irqsave(&huge->lock, irq_flags);
-                while (i < npages) {
+                while ((npages - i) >= HPAGE_PMD_NR) {
                         struct page *p = pages[i];
                         unsigned j;