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

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Message-ID: <AANLkTimNpacSqjgNN-bNdK-vOwep5LEprE_PvaEbjuDj@mail.gmail.com>
Date:	Wed, 21 Jul 2010 01:07:39 +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 Wed, Jul 21, 2010 at 1:00 AM, Alex Deucher <alexdeucher@...il.com> wrote:
> On Tue, Jul 20, 2010 at 4:13 PM, Alexander Y. Fomichev
> <git.user@...il.com> wrote:
>> 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?
>
> Those are void functions so there's nothing to return.

i mean both of them call r600_nomm_get_vb and both of them
check if (!dev_priv->blit_vb), not return  value.I mean would be
logical to check it the same way everytime r600_nomm_get_vb
gets called.

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



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