linux-kernel - Re: drivers/gpu/drm/radeon/r600_blit.c: fix possible NULL pointer derefernce

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Date:	Tue, 20 Jul 2010 13:37:23 -0400
From:	Alex Deucher <alexdeucher@...il.com>
To:	"Alexander Y. Fomichev" <git.user@...il.com>
Cc:	Dave Airlie <airlied@...hat.com>, Robert Noland <rnoland@...p.net>,
	Matt Turner <mattst88@...il.com>,
	Jerome Glisse <jglisse@...hat.com>, akpm@...ux-foundation.org,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: drivers/gpu/drm/radeon/r600_blit.c: fix possible NULL pointer 
	derefernce

On Mon, Jul 19, 2010 at 5:42 PM, Alexander Y. Fomichev
<git.user@...il.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
>
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