drivers/gpu/drm/radeon/r600_blit.c: fix possible NULL pointer derefernce

[Alex Deucher]

On Mon, Jul 19, 2010 at 5:42 PM, Alexander Y. Fomichev
<git.user at gmail.com> wrote:
> This patch fix possible NULL pointer dereference when
> r600_prepare_blit_copy tries to fill dev_priv->blit_vb->file_priv
> without check of dev_priv->blit_vb. dev_priv->blit_vb should be
> filled by r600_nomm_get_vb but latest can fail with EAGAIN.
> Addresses: https://bugzilla.kernel.org/show_bug.cgi?id=16375
>
> ---
>  drivers/gpu/drm/radeon/r600_blit.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/r600_blit.c b/drivers/gpu/drm/radeon/r600_blit.c
> index f4fb88e..0df4a2b 100644
> --- a/drivers/gpu/drm/radeon/r600_blit.c
> +++ b/drivers/gpu/drm/radeon/r600_blit.c
> @@ -541,6 +541,8 @@ r600_prepare_blit_copy(struct drm_device *dev, struct drm_file *file_priv)
>        DRM_DEBUG("\n");
>
>        r600_nomm_get_vb(dev);
> +       if (!dev_priv->blit_vb)
> +               return;

r600_prepare_blit_copy returns an int so something like this would be better:
--- a/drivers/gpu/drm/radeon/r600_blit.c
+++ b/drivers/gpu/drm/radeon/r600_blit.c
@@ -539,8 +539,10 @@ r600_prepare_blit_copy(struct drm_device *dev,
struct drm_file *file_priv)
 {
        drm_radeon_private_t *dev_priv = dev->dev_private;
        DRM_DEBUG("\n");
+       int ret = r600_nomm_get_vb(dev);

-       r600_nomm_get_vb(dev);
+       if (ret)
+               return ret;

        dev_priv->blit_vb->file_priv = file_priv;


Alex

>
>        dev_priv->blit_vb->file_priv = file_priv;
>
> --
> 1.7.1.1
>