Hi

Am 05.05.25 um 09:29 schrieb Boris Brezillon:

On Wed, 30 Apr 2025 11:07:17 +0200 Simona Vetter simona.vetter@ffwll.ch wrote:

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On Wed, Apr 16, 2025 at 11:38:03AM +0200, Simona Vetter wrote:

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On Wed, Apr 16, 2025 at 08:57:45AM +0200, Thomas Zimmermann wrote:

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Test struct drm_gem_object.import_attach to detect imported objects.

During object clenanup, 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().

v3:

• only test for import_attach (Boris)

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

Reviewed-by: Simona Vetter simona.vetter@ffwll.ch

Also quick doc request: We do have a bit of overview documentation for prime here about specifically this lifetime fun, and why there's a chain of references and hence a distinction between imported foreign dma-buf and re-imported native dma-buf:

https://dri.freedesktop.org/docs/drm/gpu/drm-mm.html#reference-counting-for-...

I think it would be good to augment this with more links to functions (like this one recently added and fixed in this patch here) and struct members to that overview. And maybe also link from key function and struct functions back to that overview doc. Otherwise I think the next person will get confused by this rather tricky code again and break a corner cases.

BTW, could we also backmerge 6.15-rc5 into drm-misc-next so the fix is also present in drm-misc-next?

drm-misc-next is now at -rc5

Best regards Thomas