From 1ae209047950c7868223df693bf19e9433b76153 Mon Sep 17 00:00:00 2001
From: Robin Murphy <robin.murphy@arm.com>
Date: Fri, 11 Nov 2016 17:59:22 +0000
Subject: iommu/arm-smmu: Fix group refcounting

When arm_smmu_device_group() finds an existing group due to Stream ID
aliasing, it should be taking an additional reference on that group.
Otherwise, the caller of iommu_group_get_for_dev() will inadvertently
remove the reference taken by iommu_group_add_device(), and the group
will be freed prematurely if any device is removed.

Reported-by: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 739f0b4..df18dac 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1484,7 +1484,7 @@ static struct iommu_group *arm_smmu_device_group(struct device *dev)
 	}
 
 	if (group)
-		return group;
+		return iommu_group_ref_get(group);
 
 	if (dev_is_pci(dev))
 		group = pci_device_group(dev);
-- 
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