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

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Message-ID: <AANLkTikTetZ9vREMFfCSmJa7f9w1cmSFk145SthSFpPu@mail.gmail.com>
Date:	Wed, 21 Jul 2010 00:13:42 +0400
From:	"Alexander Y. Fomichev" <git.user@...il.com>
To:	Alex Deucher <alexdeucher@...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 Tue, Jul 20, 2010 at 9:37 PM, Alex Deucher <alexdeucher@...il.com> wrote:
> 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
>>
>

i haven't any preferneces, the only thing is - it would be logical
to have every check in common style, so other cases
(r600_blit_copy, r600_blit_swap) should be fixed, nop?

-- 
Best regards.
       Alexander Y. Fomichev <git.user@...il.com>
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