From: Robin Murphy <robin.murphy@arm.com>
Date: Fri, 11 Nov 2016 17:59:25 +0000 (+0000)
Subject: iommu/mediatek: Fix M4Uv1 group refcounting
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=5d1d43b0f6231cfffde61f8774283f170c040776;p=linux-beck.git

iommu/mediatek: Fix M4Uv1 group refcounting

For each subsequent device assigned to the m4u_group after its initial
allocation, we need to take an additional reference. 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.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---

diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
index b8aeb0768483..c7063e9d67d8 100644
--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c
@@ -502,6 +502,8 @@ static struct iommu_group *mtk_iommu_device_group(struct device *dev)
 		data->m4u_group = iommu_group_alloc();
 		if (IS_ERR(data->m4u_group))
 			dev_err(dev, "Failed to allocate M4U IOMMU group\n");
+	} else {
+		iommu_group_ref_get(data->m4u_group);
 	}
 	return data->m4u_group;
 }