Re: [PATCH] drm/ttm: Fix an invalid freeing on already freed page in error path

["Christian König" <christian.koenig@amd.com>]

Am 21.02.24 um 08:33 schrieb Thomas Hellström:
> If caching mode change fails due to, for example, OOM we
> free the allocated pages in a two-step process. First the pages
> for which the caching change has already succeeded. Secondly
> the pages for which a caching change did not succeed.
>
> However the second step was incorrectly freeing the pages already
> freed in the first step.
>
> Fix.
>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Fixes: 379989e7cbdc ("drm/ttm/pool: Fix ttm_pool_alloc error path")
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Dave Airlie <airlied@redhat.com>
> Cc: Christian Koenig <christian.koenig@amd.com>
> Cc: Huang Rui <ray.huang@amd.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: <stable@vger.kernel.org> # v6.4+

You don't know how much time I've spend staring at this line to find the 
bug in it and haven't seen it. Got bug reports about that for month as well.

Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
>   drivers/gpu/drm/ttm/ttm_pool.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index b62f420a9f96..112438d965ff 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -387,7 +387,7 @@ static void ttm_pool_free_range(struct ttm_pool *pool, struct ttm_tt *tt,
>   				enum ttm_caching caching,
>   				pgoff_t start_page, pgoff_t end_page)
>   {
> -	struct page **pages = tt->pages;
> +	struct page **pages = &tt->pages[start_page];
>   	unsigned int order;
>   	pgoff_t i, nr;
>