drm: prime: fix refcounting on the dmabuf import error path

In commit be8a42a we inroduced a refcount problem, where on the
drm_gem_prime_fd_to_handle() error path we'll call dma_buf_put() for
self imported dma buffers.

Fix this by taking a reference on the dma buffer in the .gem_import
hook instead of assuming the caller had taken one. Besides fixing the
bug this is also more logical.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_prime.c

@@ -271,7 +271,6 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 			 * refcount on gem itself instead of f_count of dmabuf.
 			 */
 			drm_gem_object_reference(obj);
-			dma_buf_put(dma_buf);
 			return obj;
 		}
 	}
@@ -280,6 +279,8 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 	if (IS_ERR(attach))
 		return ERR_PTR(PTR_ERR(attach));
 
+	get_dma_buf(dma_buf);
+
 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
 	if (IS_ERR_OR_NULL(sgt)) {
 		ret = PTR_ERR(sgt);
@@ -300,6 +301,8 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 	dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
 fail_detach:
 	dma_buf_detach(dma_buf, attach);
+	dma_buf_put(dma_buf);
+
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(drm_gem_prime_import);
@@ -342,6 +345,9 @@ int drm_gem_prime_fd_to_handle(struct drm_device *dev,
 		goto fail;
 
 	mutex_unlock(&file_priv->prime.lock);
+
+	dma_buf_put(dma_buf);
+
 	return 0;
 
 fail:

drivers/gpu/drm/exynos/exynos_drm_dmabuf.c

@@ -235,7 +235,6 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
 			 * refcount on gem itself instead of f_count of dmabuf.
 			 */
 			drm_gem_object_reference(obj);
-			dma_buf_put(dma_buf);
 			return obj;
 		}
 	}
@@ -244,6 +243,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
 	if (IS_ERR(attach))
 		return ERR_PTR(-EINVAL);
 
+	get_dma_buf(dma_buf);
 
 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
 	if (IS_ERR_OR_NULL(sgt)) {
@@ -298,6 +298,8 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
 	dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
 err_buf_detach:
 	dma_buf_detach(dma_buf, attach);
+	dma_buf_put(dma_buf);
+
 	return ERR_PTR(ret);
 }
 

drivers/gpu/drm/i915/i915_gem_dmabuf.c

@@ -272,7 +272,6 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 			 * refcount on gem itself instead of f_count of dmabuf.
 			 */
 			drm_gem_object_reference(&obj->base);
-			dma_buf_put(dma_buf);
 			return &obj->base;
 		}
 	}
@@ -282,6 +281,8 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 	if (IS_ERR(attach))
 		return ERR_CAST(attach);
 
+	get_dma_buf(dma_buf);
+
 	obj = i915_gem_object_alloc(dev);
 	if (obj == NULL) {
 		ret = -ENOMEM;
@@ -301,5 +302,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 
 fail_detach:
 	dma_buf_detach(dma_buf, attach);
+	dma_buf_put(dma_buf);
+
 	return ERR_PTR(ret);
 }

drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c

@@ -212,7 +212,6 @@ struct drm_gem_object *omap_gem_prime_import(struct drm_device *dev,
 			 * refcount on gem itself instead of f_count of dmabuf.
 			 */
 			drm_gem_object_reference(obj);
-			dma_buf_put(buffer);
 			return obj;
 		}
 	}

drivers/gpu/drm/udl/udl_gem.c

@@ -303,6 +303,8 @@ struct drm_gem_object *udl_gem_prime_import(struct drm_device *dev,
 	if (IS_ERR(attach))
 		return ERR_CAST(attach);
 
+	get_dma_buf(dma_buf);
+
 	sg = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
 	if (IS_ERR(sg)) {
 		ret = PTR_ERR(sg);
@@ -322,5 +324,7 @@ struct drm_gem_object *udl_gem_prime_import(struct drm_device *dev,
 	dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
 fail_detach:
 	dma_buf_detach(dma_buf, attach);
+	dma_buf_put(dma_buf);
+
 	return ERR_PTR(ret);
 }