[PATCH 4.19 64/96] drm/ttm: fix out-of-bounds read in ttm_put_pages() v2

Greg Kroah-Hartman
2019-04-24T17:47:51Z

From: Christian König <christian.koenig@amd.com>

commit a66477b0efe511d98dde3e4aaeb189790e6f0a39 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/ttm/ttm_page_alloc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- 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 **
}

#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 **
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;