Test struct drm_gem_object.import_attach.dmabuf to detect imported objects. Warn if the stored state is inconsistent.

During object clenaup, the dma_buf field might be NULL. Testing it in an object's free callback then incorrectly does a cleanup as for native objects. Happens for calls to drm_mode_destroy_dumb_ioctl() that clears the dma_buf field in drm_gem_object_exported_dma_buf_free().

v2: - use import_attach.dmabuf instead of dma_buf (Christian)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Fixes: b57aa47d39e9 ("drm/gem: Test for imported GEM buffers with helper") Reported-by: Andy Yan andyshrk@163.com Closes: https://lore.kernel.org/dri-devel/38d09d34.4354.196379aa560.Coremail.andyshr... Tested-by: Andy Yan andyshrk@163.com Cc: Thomas Zimmermann tzimmermann@suse.de Cc: Anusha Srivatsa asrivats@redhat.com Cc: Christian König christian.koenig@amd.com Cc: Maarten Lankhorst maarten.lankhorst@linux.intel.com Cc: Maxime Ripard mripard@kernel.org Cc: David Airlie airlied@gmail.com Cc: Simona Vetter simona@ffwll.ch Cc: Sumit Semwal sumit.semwal@linaro.org Cc: "Christian König" christian.koenig@amd.com Cc: dri-devel@lists.freedesktop.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org --- include/drm/drm_gem.h | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h index 9b71f7a9f3f8..464b9c7feec0 100644 --- a/include/drm/drm_gem.h +++ b/include/drm/drm_gem.h @@ -579,6 +579,21 @@ static inline bool drm_gem_object_is_shared_for_memory_stats(struct drm_gem_obje return (obj->handle_count > 1) || obj->dma_buf; }

+/** + * drm_gem_owns_dma_buf() - Tests if GEM object backs a DMA-buffer object + * @obj: the GEM object + * @obj: the DMA buffer + * + * Returns: + * True if the DMA buffer refers to the GEM object's buffer. + */ +static inline bool drm_gem_owns_dma_buf(const struct drm_gem_object *obj, + const struct dma_buf *dma_buf) +{ + /* The dma-buf's priv field points to the original GEM object. */ + return dma_buf->priv == obj; +} + /** * drm_gem_is_imported() - Tests if GEM object's buffer has been imported * @obj: the GEM object @@ -588,8 +603,15 @@ 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); + const struct dma_buf *dma_buf = NULL; + + if (!obj->import_attach) + return false; + + dma_buf = obj->import_attach->dmabuf; + + /* Warn if we somehow reimported our own buffer. */ + return !drm_WARN_ON_ONCE(obj->dev, !dma_buf || drm_gem_owns_dma_buf(obj, dma_buf)); }

#ifdef CONFIG_LOCKDEP