linux-kernel - Re: [PATCH 2/2 RESEND] drm/vc4: Fix OOPSes from trying to cache a partially constructed BO.

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Date:   Thu, 2 Mar 2017 09:14:56 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Eric Anholt <eric@...olt.net>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2 RESEND] drm/vc4: Fix OOPSes from trying to cache a
 partially constructed BO.

On Wed,  1 Mar 2017 10:56:02 -0800
Eric Anholt <eric@...olt.net> wrote:

> If a CMA allocation failed, the partially constructed BO would be
> unreferenced through the normal path, and we might choose to put it in
> the BO cache.  If we then reused it before it expired from the cache,
> the kernel would OOPS.
> 
> Signed-off-by: Eric Anholt <eric@...olt.net>
> Fixes: c826a6e10644 ("drm/vc4: Add a BO cache.")

Reviewed-by: Boris Brezillon <boris.brezillon@...e-electrons.com>

> ---
>  drivers/gpu/drm/vc4/vc4_bo.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_bo.c b/drivers/gpu/drm/vc4/vc4_bo.c
> index e5c7aa935b4b..af29432a6471 100644
> --- a/drivers/gpu/drm/vc4/vc4_bo.c
> +++ b/drivers/gpu/drm/vc4/vc4_bo.c
> @@ -317,6 +317,14 @@ void vc4_free_object(struct drm_gem_object *gem_bo)
>  		goto out;
>  	}
>  
> +	/* If this object was partially constructed but CMA allocation
> +	 * had failed, just free it.
> +	 */
> +	if (!bo->base.vaddr) {
> +		vc4_bo_destroy(bo);
> +		goto out;
> +	}
> +
>  	cache_list = vc4_get_cache_list_for_size(dev, gem_bo->size);
>  	if (!cache_list) {
>  		vc4_bo_destroy(bo);