iommu/virtio: Fix freeing of incomplete domains

Calling viommu_domain_free() on a domain that hasn't been finalised (not
attached to any device, for example) can currently cause an Oops,
because we attempt to call ida_free() on ID 0, which may either be
unallocated or used by another domain.

Only initialise the vdomain->viommu pointer, which denotes a finalised
domain, at the end of a successful viommu_domain_finalise().

Fixes: edcd69ab9a32 ("iommu: Add virtio-iommu driver")
Reported-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20200326093558.2641019-3-jean-philippe@linaro.org
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 93ff586..9d5d4c9 100644 (file)
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -613,18 +613,20 @@ static int viommu_domain_finalise(struct viommu_dev *viommu,
        int ret;
        struct viommu_domain *vdomain = to_viommu_domain(domain);
 
-       vdomain->viommu         = viommu;
-       vdomain->map_flags      = viommu->map_flags;
+       ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
+                             viommu->last_domain, GFP_KERNEL);
+       if (ret < 0)
+               return ret;
+
+       vdomain->id             = (unsigned int)ret;
 
        domain->pgsize_bitmap   = viommu->pgsize_bitmap;
        domain->geometry        = viommu->geometry;
 
-       ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
-                             viommu->last_domain, GFP_KERNEL);
-       if (ret >= 0)
-               vdomain->id = (unsigned int)ret;
+       vdomain->map_flags      = viommu->map_flags;
+       vdomain->viommu         = viommu;
 
-       return ret > 0 ? 0 : ret;
+       return 0;
 }
 
 static void viommu_domain_free(struct iommu_domain *domain)