From: Johan Hovold <johan@kernel.org>
Date: Mon, 20 Oct 2025 04:53:10 +0000 (+0200)
Subject: iommu/mediatek: fix use-after-free on probe deferral
X-Git-Tag: v6.18.3~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f6c08d3aa441bbc1956e9d65f1cbb89113a5aa8a;p=thirdparty%2Fkernel%2Fstable.git

iommu/mediatek: fix use-after-free on probe deferral

commit de83d4617f9fe059623e97acf7e1e10d209625b5 upstream.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 0e0285348d2b8..319974557f325 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -1211,16 +1211,19 @@ 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,
@@ -1228,7 +1231,8 @@ 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;
 
@@ -1400,8 +1404,12 @@ out_sysfs_remove:
 	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;
@@ -1421,6 +1429,9 @@ static void 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++) {