Re: [PATCH 41/51] drm/tidss: Drop explicit drm_mode_config_cleanup call

From: Jyri Sarha <jsarha@ti.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
	DRI Development <dri-devel@lists.freedesktop.org>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Subject: Re: [PATCH 41/51] drm/tidss: Drop explicit drm_mode_config_cleanup call
Date: Sun, 23 Feb 2020 20:50:50 +0200	[thread overview]
Message-ID: <3697c192-3274-259a-d0f6-fa3f60273f43@ti.com> (raw)
In-Reply-To: <20200221210319.2245170-42-daniel.vetter@ffwll.ch>

On 21/02/2020 23:03, Daniel Vetter wrote:
> It's right above the drm_dev_put().
> 
> This is made possible by a preceeding patch which added a drmm_
> cleanup action to drm_mode_config_init(), hence all we need to do to
> ensure that drm_mode_config_cleanup() is run on final drm_device
> cleanup is check the new error code for _init().
> 
> Aside: Another driver with a bit much devm_kzalloc, which should
> probably use drmm_kzalloc instead ...
> 
> I'm pretty sure this one blows up already under KASAN because it's
> using devm_drm_dev_init, and later on devm_kzalloc. Hence the memory
> will get freed before the final drm_dev_put (all from the devres
> code), but the cleanup in that final drm_dev_put will access the just
> freed memory.
> 
> Unfortunately fixing this properly needs slightly more work, namely
> drmm_ versions for all the drm objects (planes, crtc, ...), so that
> the cleanup actually happens before even drmm_kzalloc would release
> the underlying memory. Not quite there yet.
> 
> v2: Explain why this cleanup is possible (Laurent).
> 
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Jyri Sarha <jsarha@ti.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>

Acked-by: Jyri Sarha <jsarha@ti.com>

> ---
>  drivers/gpu/drm/tidss/tidss_drv.c |  4 ----
>  drivers/gpu/drm/tidss/tidss_kms.c | 19 +++++--------------
>  drivers/gpu/drm/tidss/tidss_kms.h |  1 -
>  3 files changed, 5 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_drv.c b/drivers/gpu/drm/tidss/tidss_drv.c
> index 460d5e9d0cf4..ad449d104306 100644
> --- a/drivers/gpu/drm/tidss/tidss_drv.c
> +++ b/drivers/gpu/drm/tidss/tidss_drv.c
> @@ -103,11 +103,7 @@ static const struct dev_pm_ops tidss_pm_ops = {
>  
>  static void tidss_release(struct drm_device *ddev)
>  {
> -	struct tidss_device *tidss = ddev->dev_private;
> -
>  	drm_kms_helper_poll_fini(ddev);
> -
> -	tidss_modeset_cleanup(tidss);
>  }
>  
>  DEFINE_DRM_GEM_CMA_FOPS(tidss_fops);
> diff --git a/drivers/gpu/drm/tidss/tidss_kms.c b/drivers/gpu/drm/tidss/tidss_kms.c
> index 5311e0f1c551..87e07e0e4eae 100644
> --- a/drivers/gpu/drm/tidss/tidss_kms.c
> +++ b/drivers/gpu/drm/tidss/tidss_kms.c
> @@ -208,7 +208,9 @@ int tidss_modeset_init(struct tidss_device *tidss)
>  
>  	dev_dbg(tidss->dev, "%s\n", __func__);
>  
> -	drm_mode_config_init(ddev);
> +	ret = drm_mode_config_init(ddev);
> +	if (ret)
> +		return ret;
>  
>  	ddev->mode_config.min_width = 8;
>  	ddev->mode_config.min_height = 8;
> @@ -220,11 +222,11 @@ int tidss_modeset_init(struct tidss_device *tidss)
>  
>  	ret = tidss_dispc_modeset_init(tidss);
>  	if (ret)
> -		goto err_mode_config_cleanup;
> +		return ret;
>  
>  	ret = drm_vblank_init(ddev, tidss->num_crtcs);
>  	if (ret)
> -		goto err_mode_config_cleanup;
> +		return ret;
>  
>  	/* Start with vertical blanking interrupt reporting disabled. */
>  	for (i = 0; i < tidss->num_crtcs; ++i)
> @@ -235,15 +237,4 @@ int tidss_modeset_init(struct tidss_device *tidss)
>  	dev_dbg(tidss->dev, "%s done\n", __func__);
>  
>  	return 0;
> -
> -err_mode_config_cleanup:
> -	drm_mode_config_cleanup(ddev);
> -	return ret;
> -}
> -
> -void tidss_modeset_cleanup(struct tidss_device *tidss)
> -{
> -	struct drm_device *ddev = &tidss->ddev;
> -
> -	drm_mode_config_cleanup(ddev);
>  }
> diff --git a/drivers/gpu/drm/tidss/tidss_kms.h b/drivers/gpu/drm/tidss/tidss_kms.h
> index dda5625d0128..99aaff099f22 100644
> --- a/drivers/gpu/drm/tidss/tidss_kms.h
> +++ b/drivers/gpu/drm/tidss/tidss_kms.h
> @@ -10,6 +10,5 @@
>  struct tidss_device;
>  
>  int tidss_modeset_init(struct tidss_device *tidss);
> -void tidss_modeset_cleanup(struct tidss_device *tidss);
>  
>  #endif
> 


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