Re: [PATCH v2 2/5] iommu/mediatek: Add error path for loop of mm_dts_parse

[Robin Murphy]

On 2022-06-16 11:08, Yong Wu wrote:
> On Thu, 2022-06-16 at 09:59 +0100, Robin Murphy wrote:
> > On 2022-06-16 06:42, Yong Wu wrote:
> > > The mtk_iommu_mm_dts_parse will parse the smi larbs nodes. if the
> > > i+1
> > > larb is parsed fail(return -EINVAL), we should of_node_put for the
> > > 0..i
> > > larbs. In the fail path, one of_node_put matches with
> > > of_parse_phandle in
> > > it.
> > >
> > > Fixes: d2e9a1102cfc ("iommu/mediatek: Contain MM IOMMU flow with
> > > the MM TYPE")
> > > Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
> > > ---
> > >    drivers/iommu/mtk_iommu.c | 21 ++++++++++++++++-----
> > >    1 file changed, 16 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > > index 3b2489e8a6dd..ab24078938bf 100644
> > > --- a/drivers/iommu/mtk_iommu.c
> > > +++ b/drivers/iommu/mtk_iommu.c
> > > @@ -1071,12 +1071,12 @@ static int mtk_iommu_mm_dts_parse(struct
> > > device *dev, struct component_match **m
> > >    
> > >    		plarbdev = of_find_device_by_node(larbnode);
> > >    		if (!plarbdev) {
> > > -			of_node_put(larbnode);
> > > -			return -ENODEV;
> > > +			ret = -ENODEV;
> > > +			goto err_larbnode_put;
> > >    		}
> > >    		if (!plarbdev->dev.driver) {
> > > -			of_node_put(larbnode);
> > > -			return -EPROBE_DEFER;
> > > +			ret = -EPROBE_DEFER;
> > > +			goto err_larbnode_put;
> > >    		}
> > >    		data->larb_imu[id].dev = &plarbdev->dev;
> > >    
> > > @@ -1107,9 +1107,20 @@ static int mtk_iommu_mm_dts_parse(struct
> > > device *dev, struct component_match **m
> > >    			       DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME);
> > >    	if (!link) {
> > >    		dev_err(dev, "Unable to link %s.\n", dev_name(data-
> > > > smicomm_dev));
> > > -		return -EINVAL;
> > > +		ret = -EINVAL;
> > > +		goto err_larbnode_put;
> > >    	}
> > >    	return 0;
> > > +
> > > +err_larbnode_put:
> > > +	while (i--) {
> > > +		larbnode = of_parse_phandle(dev->of_node,
> > > "mediatek,larbs", i);
> > > +		if (larbnode && of_device_is_available(larbnode)) {
> > > +			of_node_put(larbnode);
> > > +			of_node_put(larbnode);
> > > +		}
> >
> > This looks a bit awkward - could we not just iterate through
> > data->larb_imu and put dev->of_node for each valid dev?
>
> It should work. Thanks very much.
>
> > Also, of_find_device_by_node() takes a reference on the struct
> > device
> > itself, so strictly we should be doing put_device() on those as well
> > if we're bailing out.
>
> Thanks for this hint. A new reference for me. I will add it.

In fact, thinking about it some more we may as well do the of_node_put() 
unconditionally immediately after the of_find_device_by_node() call, so 
then it's *only* the device references we'd need to worry about cleaning 
up in the failure path.

Robin.