[PATCH 3/6] VT-d: don't leak domid mapping on error path

[Jan Beulich <jbeulich@suse.com>]

While domain_context_mapping() invokes domain_context_unmap() in a sub-
case of handling DEV_TYPE_PCI when encountering an error, thus avoiding
a leak, individual calls to domain_context_mapping_one() aren't
similarly covered. Such a leak might persist until domain destruction.
Leverage that these cases can be recognized by pdev being non-NULL.

Fixes: dec403cc668f ("VT-d: fix iommu_domid for PCI/PCIx devices assignment")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
The Fixes: tag isn't strictly correct, as error handling had more severe
shortcomings at the time. But I wouldn't want to blame a commit
improving error handling to have introduced the leak.

--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1518,7 +1518,12 @@ int domain_context_mapping_one(
         rc = me_wifi_quirk(domain, bus, devfn, MAP_ME_PHANTOM_FUNC);
 
     if ( rc )
-        domain_context_unmap_one(domain, iommu, bus, devfn);
+    {
+        ret = domain_context_unmap_one(domain, iommu, bus, devfn);
+
+        if ( !ret && pdev && pdev->devfn == devfn )
+            check_cleanup_domid_map(domain, pdev, iommu);
+    }
 
     return rc;
 }