iommu: Don't overwrite domain pointer when there is no default_domain

commit eebb8034a5be8c2177cbf07ca2ecd2ff8a058958 upstream.

IOMMU drivers that do not support default domains, but make
use of the the group->domain pointer can get that pointer
overwritten with NULL on device add/remove.

Make sure this can't happen by only overwriting the domain
pointer when it is NULL.

Fixes: 1228236de5f9 ('iommu: Move default domain allocation to iommu_group_get_for_dev()')
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 0e3b0092ec92c9d4d1dcb06e713edcf99c4a9293..515bb8b8095230488f49f139c6a68c6e9381d857 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -848,7 +848,8 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev)
        if (!group->default_domain) {
                group->default_domain = __iommu_domain_alloc(dev->bus,
                                                             IOMMU_DOMAIN_DMA);
-               group->domain = group->default_domain;
+               if (!group->domain)
+                       group->domain = group->default_domain;
        }
 
        ret = iommu_group_add_device(group, dev);