[PATCH] drm/gem: fix not to assign error value to gem name

[PATCH] drm/gem: fix not to assign error value to gem name

[Seung-Woo Kim]

From: YoungJun Cho <yj44.cho@samsung.com>

If idr_alloc() is failed, obj->name can be error value. Also
it cleans up duplicated flink processing code.

Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 drivers/gpu/drm/drm_gem.c |   18 +++++++-----------
 1 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index cf919e3..239ef30 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -453,25 +453,21 @@ drm_gem_flink_ioctl(struct drm_device *dev, void *data,
 	spin_lock(&dev->object_name_lock);
 	if (!obj->name) {
 		ret = idr_alloc(&dev->object_name_idr, obj, 1, 0, GFP_NOWAIT);
-		obj->name = ret;
-		args->name = (uint64_t) obj->name;
-		spin_unlock(&dev->object_name_lock);
-		idr_preload_end();
-
 		if (ret < 0)
 			goto err;
-		ret = 0;
+
+		obj->name = ret;
 
 		/* Allocate a reference for the name table.  */
 		drm_gem_object_reference(obj);
-	} else {
-		args->name = (uint64_t) obj->name;
-		spin_unlock(&dev->object_name_lock);
-		idr_preload_end();
-		ret = 0;
 	}
 
+	args->name = (uint64_t) obj->name;
+	ret = 0;
+
 err:
+	spin_unlock(&dev->object_name_lock);
+	idr_preload_end();
 	drm_gem_object_unreference_unlocked(obj);
 	return ret;
 }
-- 
1.7.4.1

Re: [PATCH] drm/gem: fix not to assign error value to gem name

[Chris Wilson]

On Wed, Jun 26, 2013 at 10:42:39AM +0900, Seung-Woo Kim wrote:
> From: YoungJun Cho <yj44.cho@samsung.com>
> 
> If idr_alloc() is failed, obj->name can be error value. Also
> it cleans up duplicated flink processing code.

You should mention that it is a regression from
commit 2e928815c (drm: convert to idr_alloc())
 
> Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
> Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

Re: [PATCH] drm/gem: fix not to assign error value to gem name

[YoungJun Cho]

[-- Attachment #1.1: Type: text/plain, Size: 942 bytes --]

On Jun 26, 2013 5:56 PM, "Chris Wilson" <chris@chris-wilson.co.uk> wrote:
>
> On Wed, Jun 26, 2013 at 10:42:39AM +0900, Seung-Woo Kim wrote:
> > From: YoungJun Cho <yj44.cho@samsung.com>
> >
> > If idr_alloc() is failed, obj->name can be error value. Also
> > it cleans up duplicated flink processing code.
>
> You should mention that it is a regression from
> commit 2e928815c (drm: convert to idr_alloc())
>
> > Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
> > Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> > Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre
>

Thank you for comments!
I'll update commit msg.

Best regards YJ
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> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

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[PATCH v2] drm/gem: fix not to assign error value to gem name

[Seung-Woo Kim]

From: YoungJun Cho <yj44.cho@samsung.com>

If idr_alloc() is failed, obj->name can be error value. Also
it cleans up duplicated flink processing code.

This regression has been introduced in

commit 2e928815c1886fe628ed54623aa98d0889cf5509
Author: Tejun Heo <tj@kernel.org>
Date:   Wed Feb 27 17:04:08 2013 -0800

    drm: convert to idr_alloc()

Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
change since v1:
- Add a regression commit information in commit msg as Chris commented

 drivers/gpu/drm/drm_gem.c |   18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 4321713..c9d7081 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -453,25 +453,21 @@ drm_gem_flink_ioctl(struct drm_device *dev, void *data,
 	spin_lock(&dev->object_name_lock);
 	if (!obj->name) {
 		ret = idr_alloc(&dev->object_name_idr, obj, 1, 0, GFP_NOWAIT);
-		obj->name = ret;
-		args->name = (uint64_t) obj->name;
-		spin_unlock(&dev->object_name_lock);
-		idr_preload_end();
-
 		if (ret < 0)
 			goto err;
-		ret = 0;
+
+		obj->name = ret;
 
 		/* Allocate a reference for the name table.  */
 		drm_gem_object_reference(obj);
-	} else {
-		args->name = (uint64_t) obj->name;
-		spin_unlock(&dev->object_name_lock);
-		idr_preload_end();
-		ret = 0;
 	}
 
+	args->name = (uint64_t) obj->name;
+	ret = 0;
+
 err:
+	spin_unlock(&dev->object_name_lock);
+	idr_preload_end();
 	drm_gem_object_unreference_unlocked(obj);
 	return ret;
 }
-- 
1.7.9.5

Re: [PATCH v2] drm/gem: fix not to assign error value to gem name

[Chris Wilson]

On Thu, Jun 27, 2013 at 08:58:33AM +0900, Seung-Woo Kim wrote:
> From: YoungJun Cho <yj44.cho@samsung.com>
> 
> If idr_alloc() is failed, obj->name can be error value. Also
> it cleans up duplicated flink processing code.
> 
> This regression has been introduced in
> 
> commit 2e928815c1886fe628ed54623aa98d0889cf5509
> Author: Tejun Heo <tj@kernel.org>
> Date:   Wed Feb 27 17:04:08 2013 -0800
> 
>     drm: convert to idr_alloc()
> 
> Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
> Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

Minor comment inline.

> ---
> change since v1:
> - Add a regression commit information in commit msg as Chris commented
> 
>  drivers/gpu/drm/drm_gem.c |   18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 4321713..c9d7081 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -453,25 +453,21 @@ drm_gem_flink_ioctl(struct drm_device *dev, void *data,
>  	spin_lock(&dev->object_name_lock);
>  	if (!obj->name) {
>  		ret = idr_alloc(&dev->object_name_idr, obj, 1, 0, GFP_NOWAIT);
> -		obj->name = ret;
> -		args->name = (uint64_t) obj->name;
> -		spin_unlock(&dev->object_name_lock);
> -		idr_preload_end();
> -
>  		if (ret < 0)
>  			goto err;

Being pedantic, ret == 0 is also an error - but a programming error
leading to an object leak. BUG_ON(ret == 0) ?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

Re: [PATCH v2] drm/gem: fix not to assign error value to gem name

[김승우]

Hello, Chris,

On 2013년 06월 27일 17:31, Chris Wilson wrote:
> On Thu, Jun 27, 2013 at 08:58:33AM +0900, Seung-Woo Kim wrote:
>> From: YoungJun Cho <yj44.cho@samsung.com>
>>
>> If idr_alloc() is failed, obj->name can be error value. Also
>> it cleans up duplicated flink processing code.
>>
>> This regression has been introduced in
>>
>> commit 2e928815c1886fe628ed54623aa98d0889cf5509
>> Author: Tejun Heo <tj@kernel.org>
>> Date:   Wed Feb 27 17:04:08 2013 -0800
>>
>>     drm: convert to idr_alloc()
>>
>> Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
>> Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> 
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> 
> Minor comment inline.
> 
>> ---
>> change since v1:
>> - Add a regression commit information in commit msg as Chris commented
>>
>>  drivers/gpu/drm/drm_gem.c |   18 +++++++-----------
>>  1 file changed, 7 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
>> index 4321713..c9d7081 100644
>> --- a/drivers/gpu/drm/drm_gem.c
>> +++ b/drivers/gpu/drm/drm_gem.c
>> @@ -453,25 +453,21 @@ drm_gem_flink_ioctl(struct drm_device *dev, void *data,
>>  	spin_lock(&dev->object_name_lock);
>>  	if (!obj->name) {
>>  		ret = idr_alloc(&dev->object_name_idr, obj, 1, 0, GFP_NOWAIT);
>> -		obj->name = ret;
>> -		args->name = (uint64_t) obj->name;
>> -		spin_unlock(&dev->object_name_lock);
>> -		idr_preload_end();
>> -
>>  		if (ret < 0)
>>  			goto err;
> 
> Being pedantic, ret == 0 is also an error - but a programming error
> leading to an object leak. BUG_ON(ret == 0) ?
> -Chris
> 

It seems that idr_alloc() with start id 1 does not return 0, so IMHO,
ret == 0 can be ignored here.

But if you think it needs to consider programming error, I'll add some
assertion. Please let me know.

Thanks and Regards,
- Seung-Woo Kim

-- 
Seung-Woo Kim
Samsung Software R&D Center
--

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Re: [PATCH v2] drm/gem: fix not to assign error value to gem name

[Chris Wilson]

On Fri, Jun 28, 2013 at 01:15:43PM +0900, 김승우 wrote:
> > Being pedantic, ret == 0 is also an error - but a programming error
> > leading to an object leak. BUG_ON(ret == 0) ?
> > 
> 
> It seems that idr_alloc() with start id 1 does not return 0, so IMHO,
> ret == 0 can be ignored here.

Yes, it is an impossible condition, hence the suggestion of a BUG_ON().
It is a paranoid check for whether idr_alloc() fails.
 
> But if you think it needs to consider programming error, I'll add some
> assertion. Please let me know.

Successfully setting obj->name = 0 would lead to interesting confusion
in userspace, and very difficult to debug. Given that, maybe it would be
better to BUG in the kernel. If you do feel like adding it, submit it as
a separate patch, so that it is not caught up with the bugfix.
-Chris

-- 
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