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

In commit be8a42ae60 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>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 7830d8e1f212..71c7315ca00f 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/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 @@ fail_unmap:
         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: