[PATCH 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 :
  - Assumed we have single device in the IOMMU group
  - unbind device driver
  - 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")
Tested-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
---
Hi Joerg,
  This patch is on top of iommu/next branch.

-Vasant

 drivers/iommu/iommu.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 9e0228ef612b..d21d0a217bdf 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2880,7 +2880,6 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 	}
 
 	/* We must set default_domain early for __iommu_device_set_domain */
-	group->default_domain = dom;
 	if (!group->domain) {
 		/*
 		 * Drivers are not allowed to fail the first domain attach.
@@ -2896,7 +2895,6 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 		ret = __iommu_group_set_domain(group, dom);
 		if (ret) {
 			iommu_domain_free(dom);
-			group->default_domain = old_dom;
 			return ret;
 		}
 	}
@@ -2915,16 +2913,20 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 		}
 	}
 
+out_free:
+	group->default_domain = dom;
+
+	if (old_dom) {
+		iommu_domain_free(old_dom);
+		old_dom = NULL;
+	}
+
 err_restore:
 	if (old_dom) {
 		__iommu_group_set_domain_internal(
 			group, old_dom, IOMMU_SET_DOMAIN_MUST_SUCCEED);
 		iommu_domain_free(dom);
-		old_dom = NULL;
 	}
-out_free:
-	if (old_dom)
-		iommu_domain_free(old_dom);
 	return ret;
 }
 
-- 
2.31.1