[PATCH] drm/gem: Internally test import_attach for imported objects

[Thomas Zimmermann]

Test struct drm_gem_object.import_attach to detect imported objects
during cleanup. At that point, the imported DMA buffer might have
already been released and the dma_buf field is NULL. The object's
free callback then does a cleanup as for native objects.

Happens for calls to drm_mode_destroy_dumb_ioctl() that eventually
clear the dma_buf field in drm_gem_object_exported_dma_buf_free().

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Fixes: b57aa47d39e9 ("drm/gem: Test for imported GEM buffers with helper")
Reported-by: Andy Yan <andyshrk at 163.com>
Closes: https://lore.kernel.org/dri-devel/38d09d34.4354.196379aa560.Coremail.andyshrk@163.com/
Tested-by: Andy Yan <andyshrk at 163.com>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: Anusha Srivatsa <asrivats at redhat.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: David Airlie <airlied at gmail.com>
Cc: Simona Vetter <simona at ffwll.ch>
Cc: Sumit Semwal <sumit.semwal at linaro.org>
Cc: "Christian König" <christian.koenig at amd.com>
Cc: dri-devel at lists.freedesktop.org
Cc: linux-media at vger.kernel.org
Cc: linaro-mm-sig at lists.linaro.org
---
 include/drm/drm_gem.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 9b71f7a9f3f8..f09b8afcf86d 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -589,7 +589,13 @@ static inline bool drm_gem_object_is_shared_for_memory_stats(struct drm_gem_obje
 static inline bool drm_gem_is_imported(const struct drm_gem_object *obj)
 {
 	/* The dma-buf's priv field points to the original GEM object. */
-	return obj->dma_buf && (obj->dma_buf->priv != obj);
+	return (obj->dma_buf && (obj->dma_buf->priv != obj)) ||
+	       /*
+		* TODO: During object release, the dma-buf might already
+		*       be gone. For now keep testing import_attach, but
+		*       this should be removed at some point.
+		*/
+	       obj->import_attach;
 }
 
 #ifdef CONFIG_LOCKDEP
-- 
2.49.0