linux-kernel - [PATCH] iommu: Don't call .probe

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Date:   Tue, 19 May 2020 15:28:24 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     iommu@...ts.linux-foundation.org
Cc:     Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, Joerg Roedel <jroedel@...e.de>,
        Yong Wu <yong.wu@...iatek.com>
Subject: [PATCH] iommu: Don't call .probe_finalize() under group->mutex

From: Joerg Roedel <jroedel@...e.de>

The .probe_finalize() call-back of some IOMMU drivers calls into
arm_iommu_attach_device(). This function will call back into the
IOMMU core code, where it tries to take group->mutex again, resulting
in a deadlock.

As there is no reason why .probe_finalize() needs to be called under
that mutex, move it after the lock has been released to fix the
deadlock.

Cc: Yong Wu <yong.wu@...iatek.com>
Reported-by: Yong Wu <yong.wu@...iatek.com>
Fixes: deac0b3bed26 ("iommu: Split off default domain allocation from group assignment")
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/iommu.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 629d209b8e88..d5d9fcbc9714 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1683,17 +1683,8 @@ static void probe_alloc_default_domain(struct bus_type *bus,
 static int iommu_group_do_dma_attach(struct device *dev, void *data)
 {
 	struct iommu_domain *domain = data;
-	const struct iommu_ops *ops;
-	int ret;
-
-	ret = __iommu_attach_device(domain, dev);
-
-	ops = domain->ops;
-
-	if (ret == 0 && ops->probe_finalize)
-		ops->probe_finalize(dev);
 
-	return ret;
+	return __iommu_attach_device(domain, dev);
 }
 
 static int __iommu_group_dma_attach(struct iommu_group *group)
@@ -1702,6 +1693,21 @@ static int __iommu_group_dma_attach(struct iommu_group *group)
 					  iommu_group_do_dma_attach);
 }
 
+static int iommu_group_do_probe_finalize(struct device *dev, void *data)
+{
+	struct iommu_domain *domain = data;
+
+	if (domain->ops->probe_finalize)
+		domain->ops->probe_finalize(dev);
+
+	return 0;
+}
+
+static void __iommu_group_dma_finalize(struct iommu_group *group)
+{
+	__iommu_group_for_each_dev(group, group->default_domain,
+				   iommu_group_do_probe_finalize);
+}
 static int iommu_do_create_direct_mappings(struct device *dev, void *data)
 {
 	struct iommu_group *group = data;
@@ -1754,6 +1760,8 @@ int bus_iommu_probe(struct bus_type *bus)
 
 		if (ret)
 			break;
+
+		__iommu_group_dma_finalize(group);
 	}
 
 	return ret;
-- 
2.25.1