[PATCH 1/5] drm/armada: fix leak of crtc structure

[Sean Paul]

On Wed, Nov 29, 2017 at 07:16:43PM +0000, Russell King - ARM Linux wrote:
> On Wed, Nov 29, 2017 at 09:53:42AM -0500, Sean Paul wrote:
> > On Wed, Nov 29, 2017 at 11:45:43AM +0000, Russell King wrote:
> > > Fix the leak of the CRTC structure in the failure paths of
> > > armada_drm_crtc_create().
> > > 
> > > Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>
> > > ---
> > >  drivers/gpu/drm/armada/armada_crtc.c | 10 ++++++++--
> > >  1 file changed, 8 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/armada/armada_crtc.c b/drivers/gpu/drm/armada/armada_crtc.c
> > > index 2e065facdce7..844d488b6654 100644
> > > --- a/drivers/gpu/drm/armada/armada_crtc.c
> > > +++ b/drivers/gpu/drm/armada/armada_crtc.c
> > > @@ -1246,11 +1246,14 @@ static int armada_drm_crtc_create(struct drm_device *drm, struct device *dev,
> > >  	dcrtc->crtc.port = port;
> > >  
> > >  	primary = kzalloc(sizeof(*primary), GFP_KERNEL);
> > > -	if (!primary)
> > > +	if (!primary) {
> > > +		kfree(dcrtc);
> > >  		return -ENOMEM;
> > > +	}
> > >  
> > >  	ret = armada_drm_plane_init(primary);
> > >  	if (ret) {
> > > +		kfree(dcrtc);
> > >  		kfree(primary);
> > >  		return ret;
> > >  	}
> > > @@ -1262,14 +1265,17 @@ static int armada_drm_crtc_create(struct drm_device *drm, struct device *dev,
> > >  				       NULL,
> > >  				       DRM_PLANE_TYPE_PRIMARY, NULL);
> > >  	if (ret) {
> > > +		kfree(dcrtc);
> > >  		kfree(primary);
> > >  		return ret;
> > >  	}
> > >  
> > >  	ret = drm_crtc_init_with_planes(drm, &dcrtc->crtc, &primary->base, NULL,
> > >  					&armada_crtc_funcs, NULL);
> > > -	if (ret)
> > > +	if (ret) {
> > > +		kfree(dcrtc);
> > >  		goto err_crtc_init;
> > 
> > The mixed use of cleaning up at every exit and the lone label is a bit messy and
> > prone to bugs such as the one you're fixing. How about you label everything
> > and then just clean up once?
> 
> It's not that simple - see alternative patch below.  How we clean
> stuff up depends on how far through the initialisation we are, and
> that doesn't lend itself to a sequential cleanup methodology.

It can be that simple, depending on how you setup your initialization sequence.
For instance, if armada_plane_init did the allocation as well as
universal_plane_init (like armada_overlay_plane_create already does), then you
wouldn't need to worry about kfree(primary) at all.

> 
> > It also seems like you're missing cleanup if armada_overlay_plane_create()
> > fails?
> 
> It's not missing.  At that point, the CRTC has been registered, and any
> failure will be cleaned up by the drm_mode_config_cleanup() in the
> error paths in armada_drm_bind() in armada_drv.c
> 
> It's rather non-obvious because it uses the ->destroy callbacks.

Got it, thanks!

Sean

> 
> diff --git a/drivers/gpu/drm/armada/armada_crtc.c b/drivers/gpu/drm/armada/armada_crtc.c
> index d987198a2ac6..79ce877bf45f 100644
> --- a/drivers/gpu/drm/armada/armada_crtc.c
> +++ b/drivers/gpu/drm/armada/armada_crtc.c
> @@ -1225,17 +1225,13 @@ static int armada_drm_crtc_create(struct drm_device *drm, struct device *dev,
>  
>  	ret = devm_request_irq(dev, irq, armada_drm_irq, 0, "armada_drm_crtc",
>  			       dcrtc);
> -	if (ret < 0) {
> -		kfree(dcrtc);
> -		return ret;
> -	}
> +	if (ret < 0)
> +		goto err_crtc;
>  
>  	if (dcrtc->variant->init) {
>  		ret = dcrtc->variant->init(dcrtc, dev);
> -		if (ret) {
> -			kfree(dcrtc);
> -			return ret;
> -		}
> +		if (ret)
> +			goto err_crtc;
>  	}
>  
>  	/* Ensure AXI pipeline is enabled */
> @@ -1247,15 +1243,14 @@ static int armada_drm_crtc_create(struct drm_device *drm, struct device *dev,
>  
>  	primary = kzalloc(sizeof(*primary), GFP_KERNEL);
>  	if (!primary) {
> -		kfree(dcrtc);
> -		return -ENOMEM;
> +		ret = -ENOMEM;
> +		goto err_crtc;
>  	}
>  
>  	ret = armada_drm_plane_init(primary);
>  	if (ret) {
> -		kfree(dcrtc);
>  		kfree(primary);
> -		return ret;
> +		goto err_crtc;
>  	}
>  
>  	ret = drm_universal_plane_init(drm, &primary->base, 0,
> @@ -1265,17 +1260,14 @@ static int armada_drm_crtc_create(struct drm_device *drm, struct device *dev,
>  				       NULL,
>  				       DRM_PLANE_TYPE_PRIMARY, NULL);
>  	if (ret) {
> -		kfree(dcrtc);
>  		kfree(primary);
> -		return ret;
> +		goto err_crtc;
>  	}
>  
>  	ret = drm_crtc_init_with_planes(drm, &dcrtc->crtc, &primary->base, NULL,
>  					&armada_crtc_funcs, NULL);
> -	if (ret) {
> -		kfree(dcrtc);
> +	if (ret)
>  		goto err_crtc_init;
> -	}
>  
>  	drm_crtc_helper_add(&dcrtc->crtc, &armada_crtc_helper_funcs);
>  
> @@ -1288,6 +1280,9 @@ static int armada_drm_crtc_create(struct drm_device *drm, struct device *dev,
>  
>  err_crtc_init:
>  	primary->base.funcs->destroy(&primary->base);
> +err_crtc:
> +	kfree(dcrtc);
> +
>  	return ret;
>  }
>  
> 
> 
> -- 
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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-- 
Sean Paul, Software Engineer, Google / Chromium OS