[PATCH v2 iommu/next] iommu: Fix default domain setup

[Vasant Hegde <vasant.hegde@amd.com>]

Commit 1000dccd5d13 ("iommu: Allow IOMMU_RESV_DIRECT to work on ARM")
accidently restored "group->domain" to "old_domain" while keeping
"group->default_domain" to new domain. Also freed new domain.

This works fine during boot as 'old_domain' is NULL. But if we try
change domain via sysfs using below command then kernel crashes with
"kernel NULL pointer dereference".

Change domain command :
  - Go to /sys/kernel/iommu_groups/<group id>/
  - Unbind device driver for all devices in the group
  - echo "<dom type>" > /sys/kernel/iommu_groups/<group id>/type

Fix above described issue by handling error path properly.

Reported-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
Fixes: 1000dccd5d13 ("iommu: Allow IOMMU_RESV_DIRECT to work on ARM")
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Tested-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
---
Changes in v2:
  - Addressed review comments from Baolu

@Joerg,
  This patch applies on top of iommu/next branch.

-Vasant
 drivers/iommu/iommu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 9e0228ef612b..e74e45f42c75 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2915,10 +2915,15 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 		}
 	}
 
+	if (old_dom)
+		iommu_domain_free(old_dom);
+	return ret;
+
 err_restore:
 	if (old_dom) {
 		__iommu_group_set_domain_internal(
 			group, old_dom, IOMMU_SET_DOMAIN_MUST_SUCCEED);
+		group->default_domain = old_dom;
 		iommu_domain_free(dom);
 		old_dom = NULL;
 	}
-- 
2.31.1