[PATCH 6.1.y 2/2] iommu/mediatek: fix use-after-free on probe deferral

[Sasha Levin <sashal@kernel.org>]

From: Johan Hovold <johan@kernel.org>

[ Upstream commit de83d4617f9fe059623e97acf7e1e10d209625b5 ]

The driver is dropping the references taken to the larb devices during
probe after successful lookup as well as on errors. This can
potentially lead to a use-after-free in case a larb device has not yet
been bound to its driver so that the iommu driver probe defers.

Fix this by keeping the references as expected while the iommu driver is
bound.

Fixes: 26593928564c ("iommu/mediatek: Add error path for loop of mm_dts_parse")
Cc: stable@vger.kernel.org
Cc: Yong Wu <yong.wu@mediatek.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/mtk_iommu.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 773cbd63ed5c..6e8294985c1f 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -1132,16 +1132,19 @@ static int mtk_iommu_mm_dts_parse(struct device *dev, struct component_match **m
 		}
 
 		component_match_add(dev, match, component_compare_dev, &plarbdev->dev);
-		platform_device_put(plarbdev);
 	}
 
-	if (!frst_avail_smicomm_node)
-		return -EINVAL;
+	if (!frst_avail_smicomm_node) {
+		ret = -EINVAL;
+		goto err_larbdev_put;
+	}
 
 	pcommdev = of_find_device_by_node(frst_avail_smicomm_node);
 	of_node_put(frst_avail_smicomm_node);
-	if (!pcommdev)
-		return -ENODEV;
+	if (!pcommdev) {
+		ret = -ENODEV;
+		goto err_larbdev_put;
+	}
 	data->smicomm_dev = &pcommdev->dev;
 
 	link = device_link_add(data->smicomm_dev, dev,
@@ -1149,7 +1152,8 @@ static int mtk_iommu_mm_dts_parse(struct device *dev, struct component_match **m
 	platform_device_put(pcommdev);
 	if (!link) {
 		dev_err(dev, "Unable to link %s.\n", dev_name(data->smicomm_dev));
-		return -EINVAL;
+		ret = -EINVAL;
+		goto err_larbdev_put;
 	}
 	return 0;
 
@@ -1320,8 +1324,12 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 	iommu_device_sysfs_remove(&data->iommu);
 out_list_del:
 	list_del(&data->list);
-	if (MTK_IOMMU_IS_TYPE(data->plat_data, MTK_IOMMU_TYPE_MM))
+	if (MTK_IOMMU_IS_TYPE(data->plat_data, MTK_IOMMU_TYPE_MM)) {
 		device_link_remove(data->smicomm_dev, dev);
+
+		for (i = 0; i < MTK_LARB_NR_MAX; i++)
+			put_device(data->larb_imu[i].dev);
+	}
 out_runtime_disable:
 	pm_runtime_disable(dev);
 	return ret;
@@ -1341,6 +1349,9 @@ static int mtk_iommu_remove(struct platform_device *pdev)
 	if (MTK_IOMMU_IS_TYPE(data->plat_data, MTK_IOMMU_TYPE_MM)) {
 		device_link_remove(data->smicomm_dev, &pdev->dev);
 		component_master_del(&pdev->dev, &mtk_iommu_com_ops);
+
+		for (i = 0; i < MTK_LARB_NR_MAX; i++)
+			put_device(data->larb_imu[i].dev);
 	}
 	pm_runtime_disable(&pdev->dev);
 	for (i = 0; i < data->plat_data->banks_num; i++) {
-- 
2.51.0