[PATCH 1/2] drm/ttm: fix out-of-bounds read in ttm_put_pages() v2

[Zhang, Jerry(Junwei)]

On 4/8/19 9:13 PM, Christian König wrote:
> 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).
Series is Reviewed-by: Junwei Zhang <Jerry.Zhang at amd.com>

Regards,
Jerry
>
> Signed-off-by: Jann Horn <jannh at google.com>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> Fixes: 5c42c64f7d54 ("drm/ttm: fix the fix for huge compound pages")
> Cc: stable at vger.kernel.org
> ---
>   drivers/gpu/drm/ttm/ttm_page_alloc.c | 5 +++--
>   1 file 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;
>