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Wed, 26 Mar 2025 06:11:01 -0700 (PDT) Date: Wed, 26 Mar 2025 13:10:58 +0000 From: Chris Bainbridge To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Danilo Krummrich , nouveau@lists.freedesktop.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, lyude@redhat.com, sumit.semwal@linaro.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] drm/prime: fix drm_prime_gem_destroy comment Message-ID: References: <00e4d9c4-ecfc-4784-b603-12db04cda806@amd.com> <1f4a534f-8883-4793-b191-60c2773f6217@amd.com> <94eeb36a-9aa5-4afd-9ba6-76e8ace10122@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <94eeb36a-9aa5-4afd-9ba6-76e8ace10122@amd.com> Content-Type: text/plain; charset="utf-8" Edit the comments on correct usage of drm_prime_gem_destroy to note that, if using TTM, drm_prime_gem_destroy must be called in the ttm_buffer_object.destroy hook, to avoid the dma_buf being freed leaving a dangling pointer which will be later dereferenced by ttm_bo_delayed_delete. Signed-off-by: Chris Bainbridge Suggested-by: Christian K=C3=B6nig --- drivers/gpu/drm/drm_prime.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index 32a8781cfd67..452d5c7cd292 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -929,7 +929,9 @@ EXPORT_SYMBOL(drm_gem_prime_export); * &drm_driver.gem_prime_import_sg_table internally. * * Drivers must arrange to call drm_prime_gem_destroy() from their - * &drm_gem_object_funcs.free hook when using this function. + * &drm_gem_object_funcs.free hook or &ttm_buffer_object.destroy + * hook when using this function, to avoid the dma_buf being freed while t= he + * ttm_buffer_object can still dereference it. */ struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev, struct dma_buf *dma_buf, @@ -999,7 +1001,9 @@ EXPORT_SYMBOL(drm_gem_prime_import_dev); * implementation in drm_gem_prime_fd_to_handle(). * * Drivers must arrange to call drm_prime_gem_destroy() from their - * &drm_gem_object_funcs.free hook when using this function. + * &drm_gem_object_funcs.free hook or &ttm_buffer_object.destroy + * hook when using this function, to avoid the dma_buf being freed while t= he + * ttm_buffer_object can still dereference it. */ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev, struct dma_buf *dma_buf) --=20 2.47.2