> -----Original Message----- > From: Inki Dae <[email protected]> > Sent: Monday, November 10, 2025 2:22 PM > To: Hoyoung Lee <[email protected]> > Cc: Seung-Woo Kim <[email protected]>; Kyungmin Park > <[email protected]>; David Airlie <[email protected]>; Simona > Vetter <[email protected]>; Krzysztof Kozlowski <[email protected]>; Alim > Akhtar <[email protected]>; [email protected]; linux- > [email protected]; [email protected]; linux- > [email protected] > Subject: Re: [PATCH 2/3] drm/exynos: Convert to drmm_mode_config_init() > and drop manual cleanup > > 2025년 9월 29일 (월) 오후 1:54, Hoyoung Lee <[email protected]>님이 작 > 성: > > > > Switch mode-config initialization to drmm_mode_config_init() so that > > the lifetime is tied to drm_device. Remove explicit > > drm_mode_config_cleanup() from error and unbind paths since cleanup is > now managed by DRM. > > > > No functional change intended. > > > > Signed-off-by: Hoyoung Lee <[email protected]> > > --- > > drivers/gpu/drm/exynos/exynos_drm_drv.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.c > > b/drivers/gpu/drm/exynos/exynos_drm_drv.c > > index 6cc7bf77bcac..1aea71778ab1 100644 > > --- a/drivers/gpu/drm/exynos/exynos_drm_drv.c > > +++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c > > @@ -257,7 +257,7 @@ static int exynos_drm_bind(struct device *dev) > > dev_set_drvdata(dev, drm); > > drm->dev_private = (void *)private; > > > > - drm_mode_config_init(drm); > > + drmm_mode_config_init(drm); > > > > exynos_drm_mode_config_init(drm); > > > > @@ -297,7 +297,6 @@ static int exynos_drm_bind(struct device *dev) > > err_unbind_all: > > component_unbind_all(drm->dev, drm); > > err_mode_config_cleanup: > > - drm_mode_config_cleanup(drm); > > In the current implementation, there is a potential dereference issue > because the private object may be freed before to_dma_dev(dev) is called. > When drmm_mode_config_init() is invoked, it registers > drm_mode_config_cleanup() as a managed action. This means that the cleanup > function will be automatically executed later when > drm_dev_put() is called. > > The problem arises when drm_dev_put() is called without explicitly > invoking drm_mode_config_cleanup() first, as in the original code. In that > case, the managed cleanup is performed later, which allows > to_dma_dev(dev) to be called after the private object has already been > released. > > For reference, the following sequence may occur internally when > drm_mode_config_cleanup() is executed: > 1. drm_mode_config_cleanup() is called. > 2. During the cleanup of FBs, planes, CRTCs, encoders, and connectors, > framebuffers or GEM objects may be released. > 3. At this point, Exynos-specific code could invoke to_dma_dev(dev). > > Therefore, the private object must remain valid until > drm_mode_config_cleanup() completes. > It would be safer to adjust the code so that kfree(private) is performed > after drm_dev_put(drm) to ensure the private data remains available during > cleanup. > > Thanks, > Inki Dae > > > exynos_drm_cleanup_dma(drm); > > kfree(private); > > dev_set_drvdata(dev, NULL); > > @@ -317,7 +316,6 @@ static void exynos_drm_unbind(struct device *dev) > > drm_atomic_helper_shutdown(drm); > > > > component_unbind_all(drm->dev, drm); > > - drm_mode_config_cleanup(drm); > > Ditto. > > > exynos_drm_cleanup_dma(drm); > > > > kfree(drm->dev_private); > > -- > > 2.34.1 > > > >
Hi, Inki Thanks for the review and for pointing out the to_dma_dev() path If I understand you correctly, fine with using DRMM, but kfree(priv) should occur after drm_dev_put(drm) That would mean releasing the drm_device first and freeing dev_private afterwards. Of course, we will also need to adjust the probe() error-unwind (err_free) order accordingly. Do you anticipate any side effects from this ordering change? I’d appreciate your thoughts. BRs, Hoyoung Lee
