linux-kernel - [PATCH v2 3/6] iommu: Same critical region for device release and removal

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Message-Id: <20230217094736.159005-4-baolu.lu@linux.intel.com>
Date:   Fri, 17 Feb 2023 17:47:33 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     iommu@...ts.linux.dev
Cc:     Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        linux-kernel@...r.kernel.org, Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v2 3/6] iommu: Same critical region for device release and removal

In a non-driver context, it is crucial to ensure the consistency of a
device's iommu ops. Otherwise, it may result in a situation where a
device is released but it's iommu ops are still used.

Put the ops->release_device and __iommu_group_remove_device() in a some
group->mutext critical region, so that, as long as group->mutex is held
and the device is in its group's device list, its iommu ops are always
consistent.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/iommu.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 6247883991e2..093692308b80 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -101,6 +101,10 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
 static struct iommu_group *iommu_group_get_for_dev(struct device *dev);
 static ssize_t iommu_group_store_type(struct iommu_group *group,
 				      const char *buf, size_t count);
+static struct group_device *
+__iommu_group_remove_device(struct iommu_group *group, struct device *dev);
+static void __iommu_group_release_device(struct iommu_group *group,
+					 struct group_device *grp_dev);
 
 #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store)		\
 struct iommu_group_attribute iommu_group_attr_##_name =		\
@@ -466,18 +470,25 @@ int iommu_probe_device(struct device *dev)
 
 void iommu_release_device(struct device *dev)
 {
+	struct iommu_group *group = dev->iommu_group;
+	struct group_device *device;
 	const struct iommu_ops *ops;
 
-	if (!dev->iommu)
+	if (!dev->iommu || !group)
 		return;
 
 	iommu_device_unlink(dev->iommu->iommu_dev, dev);
 
+	mutex_lock(&group->mutex);
 	ops = dev_iommu_ops(dev);
 	if (ops->release_device)
 		ops->release_device(dev);
+	device = __iommu_group_remove_device(group, dev);
+	mutex_unlock(&group->mutex);
+
+	if (device)
+		__iommu_group_release_device(group, device);
 
-	iommu_group_remove_device(dev);
 	module_put(ops->owner);
 	dev_iommu_free(dev);
 }
-- 
2.34.1