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

[PATCH] 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'

drm_client_buffer_delete() frees the buffer so remove the extra free.

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>
---
 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..83b294ae3e4e 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -242,8 +242,10 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
 	dumb_args.height = height;
 	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;
+	if (ret) {
+		kfree(buffer);
+		return ERR_PTR(ret);
+	}
 
 	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] drm/client: Fix double free in error path

[Daniel Vetter]

On Thu, Jul 12, 2018 at 11:18:40AM +0200, Noralf Trønnes wrote:
> This fixes a static checker warning:
> 
> 	drivers/gpu/drm/drm_client.c:289 drm_client_buffer_create()
> 	error: double free of 'buffer'
> 
> drm_client_buffer_delete() frees the buffer so remove the extra free.
> 
> 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>

You could also put an if (buffer->handle) into drm_client_buffer_delete
and simplify the code even more. handle == 0 is the canonical invalid
handle - all our idr start at 1. But this works too. On either approach:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  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..83b294ae3e4e 100644
> --- a/drivers/gpu/drm/drm_client.c
> +++ b/drivers/gpu/drm/drm_client.c
> @@ -242,8 +242,10 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
>  	dumb_args.height = height;
>  	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;
> +	if (ret) {
> +		kfree(buffer);
> +		return ERR_PTR(ret);
> +	}
>  
>  	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
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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