iommu: Check for deferred attach in iommu_group_do_dma_attach()

The iommu_group_do_dma_attach() must not attach devices which have
deferred_attach set. Otherwise devices could cause IOMMU faults when
re-initialized in a kdump kernel.

Fixes: deac0b3 ("iommu: Split off default domain allocation from group assignment")
Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Link: https://lore.kernel.org/r/20200604091944.26402-1-joro@8bytes.org

drivers/iommu/iommu.c

@@ -1680,8 +1680,12 @@ static void probe_alloc_default_domain(struct bus_type *bus,
 static int iommu_group_do_dma_attach(struct device *dev, void *data)
 {
 	struct iommu_domain *domain = data;
+	int ret = 0;
 
-	return __iommu_attach_device(domain, dev);
+	if (!iommu_is_attach_deferred(domain, dev))
+		ret = __iommu_attach_device(domain, dev);
+
+	return ret;
 }
 
 static int __iommu_group_dma_attach(struct iommu_group *group)