drm/i915/gvt: fix dropping obj reference twice

The reference count of obj will be decremented twice if error occurs in dma_buf_fd(). Additionally, attempting to read the reference count of obj after dropping reference may lead to a use after free bug. Here, we drop obj's reference until it is not used. Fixes: e546e28 ("drm/i915/gvt: Dmabuf support for GVT-g") Signed-off-by: Pan Bian <[email protected]> Reviewed-by: Zhenyu Wang <[email protected]> Signed-off-by: Zhenyu Wang <[email protected]>
josf · Nov 8, 2019 · 41d9314 · 41d9314
1 parent ee2c5ef
commit 41d9314
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/drivers/gpu/drm/i915/gvt/dmabuf.c b/drivers/gpu/drm/i915/gvt/dmabuf.c
@@ -498,8 +498,6 @@ int intel_vgpu_get_dmabuf(struct intel_vgpu *vgpu, unsigned int dmabuf_id)
 		goto out_free_gem;
 	}
 
-	i915_gem_object_put(obj);
-
 	ret = dma_buf_fd(dmabuf, DRM_CLOEXEC | DRM_RDWR);
 	if (ret < 0) {
 		gvt_vgpu_err("create dma-buf fd failed ret:%d\n", ret);
@@ -524,6 +522,8 @@ int intel_vgpu_get_dmabuf(struct intel_vgpu *vgpu, unsigned int dmabuf_id)
 		    file_count(dmabuf->file),
 		    kref_read(&obj->base.refcount));
 
+	i915_gem_object_put(obj);
+
 	return dmabuf_fd;
 
 out_free_dmabuf: