[PATCH 4.1 063/123] iommu/vt-d: Fix VM domain ID leak

From: Greg Kroah-Hartman
Date: Sat Aug 08 2015 - 18:36:30 EST

4.1-stable review patch. If anyone has any objections, please let me know.


From: Alex Williamson <alex.williamson@xxxxxxxxxx>

commit 46ebb7af7b93792de65e124e1ab8b89a108a41f2 upstream.

This continues the attempt to fix commit fb170fb4c548 ("iommu/vt-d:
Introduce helper functions to make code symmetric for readability").
The previous attempt in commit 71684406905f ("iommu/vt-d: Detach
domain *only* from attached iommus") overlooked the fact that
dmar_domain.iommu_bmp gets cleared for VM domains when devices are


The domain is detached from the iommu, but the iommu is still attached
to the domain, for whatever reason. Thus when we get to domain_exit(),
we can't rely on iommu_bmp for VM domains to find the active iommus,
we must check them all. Without that, the corresponding bit in
intel_iommu.domain_ids doesn't get cleared and repeated VM domain
creation and destruction will run out of domain IDs. Meanwhile we
still can't call iommu_detach_domain() on arbitrary non-VM domains or
we risk clearing in-use domain IDs, as 71684406905f attempted to

It's tempting to modify iommu_detach_domain() to test the domain
iommu_bmp, but the call ordering from domain_remove_one_dev_info()
prevents it being able to work as fb170fb4c548 seems to have intended.
Caching of unused VM domains on the iommu object seems to be the root
of the problem, but this code is far too fragile for that kind of
rework to be proposed for stable, so we simply revert this chunk to
its state prior to fb170fb4c548.

Fixes: fb170fb4c548 ("iommu/vt-d: Introduce helper functions to make
code symmetric for readability")
Fixes: 71684406905f ("iommu/vt-d: Detach domain *only* from attached
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Cc: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/iommu/intel-iommu.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1756,8 +1756,9 @@ static int domain_init(struct dmar_domai

static void domain_exit(struct dmar_domain *domain)
+ struct dmar_drhd_unit *drhd;
+ struct intel_iommu *iommu;
struct page *freelist = NULL;
- int i;

/* Domain 0 is reserved, so dont process it */
if (!domain)
@@ -1777,8 +1778,10 @@ static void domain_exit(struct dmar_doma

/* clear attached or cached domains */
- for_each_set_bit(i, domain->iommu_bmp, g_num_of_iommus)
- iommu_detach_domain(domain, g_iommus[i]);
+ for_each_active_iommu(iommu, drhd)
+ if (domain_type_is_vm(domain) ||
+ test_bit(iommu->seq_id, domain->iommu_bmp))
+ iommu_detach_domain(domain, iommu);


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