[PATCH v2] drm/client: Fix double free in error path

[PATCH v2] drm/client: Fix double free in error path

[Noralf Trønnes]

This fixes a static checker warning:

	drivers/gpu/drm/drm_client.c:289 drm_client_buffer_create()
	error: double free of 'buffer'

Extend drm_client_buffer_delete() to handle the case when there's no
dumb buffer attached and drop the extra kfree.

Fixes: c76f0f7cb546 ("drm: Begin an API for in-kernel clients")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---

Changes since version 1:
- Let drm_client_buffer_delete() handle all freeing (Daniel Vetter)

 drivers/gpu/drm/drm_client.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index 9b142f58d489..baff50a4c234 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -218,7 +218,9 @@ static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
 	if (buffer->gem)
 		drm_gem_object_put_unlocked(buffer->gem);
 
-	drm_mode_destroy_dumb(dev, buffer->handle, buffer->client->file);
+	if (buffer->handle)
+		drm_mode_destroy_dumb(dev, buffer->handle, buffer->client->file);
+
 	kfree(buffer);
 }
 
@@ -243,7 +245,7 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
 	dumb_args.bpp = drm_format_plane_cpp(format, 0) * 8;
 	ret = drm_mode_create_dumb(dev, &dumb_args, client->file);
 	if (ret)
-		goto err_free;
+		goto err_delete;
 
 	buffer->handle = dumb_args.handle;
 	buffer->pitch = dumb_args.pitch;
@@ -276,8 +278,6 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
 
 err_delete:
 	drm_client_buffer_delete(buffer);
-err_free:
-	kfree(buffer);
 
 	return ERR_PTR(ret);
 }
-- 
2.15.1

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Re: [PATCH v2] drm/client: Fix double free in error path

[Noralf Trønnes]

Den 12.07.2018 17.04, skrev Noralf Trønnes:
> This fixes a static checker warning:
>
> 	drivers/gpu/drm/drm_client.c:289 drm_client_buffer_create()
> 	error: double free of 'buffer'
>
> Extend drm_client_buffer_delete() to handle the case when there's no
> dumb buffer attached and drop the extra kfree.
>
> Fixes: c76f0f7cb546 ("drm: Begin an API for in-kernel clients")
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>
> Changes since version 1:
> - Let drm_client_buffer_delete() handle all freeing (Daniel Vetter)

Applied, thanks for review and an improved solution.

Noralf.

>   drivers/gpu/drm/drm_client.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> index 9b142f58d489..baff50a4c234 100644
> --- a/drivers/gpu/drm/drm_client.c
> +++ b/drivers/gpu/drm/drm_client.c
> @@ -218,7 +218,9 @@ static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
>   	if (buffer->gem)
>   		drm_gem_object_put_unlocked(buffer->gem);
>   
> -	drm_mode_destroy_dumb(dev, buffer->handle, buffer->client->file);
> +	if (buffer->handle)
> +		drm_mode_destroy_dumb(dev, buffer->handle, buffer->client->file);
> +
>   	kfree(buffer);
>   }
>   
> @@ -243,7 +245,7 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
>   	dumb_args.bpp = drm_format_plane_cpp(format, 0) * 8;
>   	ret = drm_mode_create_dumb(dev, &dumb_args, client->file);
>   	if (ret)
> -		goto err_free;
> +		goto err_delete;
>   
>   	buffer->handle = dumb_args.handle;
>   	buffer->pitch = dumb_args.pitch;
> @@ -276,8 +278,6 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
>   
>   err_delete:
>   	drm_client_buffer_delete(buffer);
> -err_free:
> -	kfree(buffer);
>   
>   	return ERR_PTR(ret);
>   }

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