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

On 2022-06-16 11:08, Yong Wu wrote:

On Thu, 2022-06-16 at 09:59 +0100, Robin Murphy wrote:

quoted

On 2022-06-16 06:42, Yong Wu wrote:

quoted

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@mediatek.com>
---
   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-

quoted

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.

quoted

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.

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