linux-kernel - [PATCH v2 5/9] iommu/of: Take a ref to the IOMMU driver during ->of

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Date:   Fri,  8 Nov 2019 15:16:04 +0000
From:   Will Deacon <will@...nel.org>
To:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Cc:     Will Deacon <will@...nel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        John Garry <john.garry@...wei.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Saravana Kannan <saravanak@...gle.com>,
        "Isaac J. Manjarres" <isaacm@...eaurora.org>,
        Robin Murphy <robin.murphy@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Joerg Roedel <joro@...tes.org>
Subject: [PATCH v2 5/9] iommu/of: Take a ref to the IOMMU driver during ->of_xlate()

Ensure that we hold a reference to the IOMMU driver module while calling
the '->of_xlate()' callback during early device probing.

Signed-off-by: Will Deacon <will@...nel.org>
---
 drivers/iommu/of_iommu.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 78faa9f73a91..25491403a0bd 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -8,6 +8,7 @@
 #include <linux/export.h>
 #include <linux/iommu.h>
 #include <linux/limits.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_iommu.h>
 #include <linux/of_pci.h>
@@ -89,16 +90,16 @@ static int of_iommu_xlate(struct device *dev,
 {
 	const struct iommu_ops *ops;
 	struct fwnode_handle *fwnode = &iommu_spec->np->fwnode;
-	int err;
+	int ret;
 
 	ops = iommu_ops_from_fwnode(fwnode);
 	if ((ops && !ops->of_xlate) ||
 	    !of_device_is_available(iommu_spec->np))
 		return NO_IOMMU;
 
-	err = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops);
-	if (err)
-		return err;
+	ret = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops);
+	if (ret)
+		return ret;
 	/*
 	 * The otherwise-empty fwspec handily serves to indicate the specific
 	 * IOMMU device we're waiting for, which will be useful if we ever get
@@ -107,7 +108,12 @@ static int of_iommu_xlate(struct device *dev,
 	if (!ops)
 		return driver_deferred_probe_check_state(dev);
 
-	return ops->of_xlate(dev, iommu_spec);
+	if (!try_module_get(ops->owner))
+		return -ENODEV;
+
+	ret = ops->of_xlate(dev, iommu_spec);
+	module_put(ops->owner);
+	return ret;
 }
 
 struct of_pci_iommu_alias_info {
-- 
2.24.0.rc1.363.gb1bccd3e3d-goog