[PATCH 0/2] intel-iommu: Fix domain_ids exhaustion

[PATCH 0/2] intel-iommu: Fix domain_ids exhaustion

[Alex Williamson]

When we unbind a device from a driver, we don't properly unlink
the domain from the iommu, so we never free the domain id it
was using.  We're typically limited to something like 256 domain
ids, so a loop of unbinding and rebinding a device can exhaust
this pretty quickly.  If we're assigning the device to a KVM
guest, libvirt does exactly this each time the device is removed
from the host driver or added back.  When we do run out, we oops
the kernel.  Fix these.  Thanks,

Alex

---

Alex Williamson (2):
      intel-iommu: Fix get_domain_for_dev() error path
      intel-iommu: Unlink domain from iommu


 drivers/pci/intel-iommu.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

[PATCH 1/2] intel-iommu: Unlink domain from iommu

[Alex Williamson]

When we remove a device, we unlink the iommu from the domain, but
we never do the reverse unlinking of the domain from the iommu.
This means that we never clear iommu->domain_ids, eventually leading
to resource exhaustion if we repeatedly bind and unbind a device
to a driver.  Also free empty domains to avoid a resource leak.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 drivers/pci/intel-iommu.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 4789f8e..8bc56c1 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -3260,8 +3260,11 @@ static int device_notifier(struct notifier_block *nb,
 	if (!domain)
 		return 0;
 
-	if (action == BUS_NOTIFY_UNBOUND_DRIVER && !iommu_pass_through)
+	if (action == BUS_NOTIFY_UNBOUND_DRIVER && !iommu_pass_through) {
 		domain_remove_one_dev_info(domain, pdev);
+		if (list_empty(&domain->devices))
+			domain_exit(domain);
+	}
 
 	return 0;
 }
@@ -3411,6 +3414,11 @@ static void domain_remove_one_dev_info(struct dmar_domain *domain,
 		domain->iommu_count--;
 		domain_update_iommu_cap(domain);
 		spin_unlock_irqrestore(&domain->iommu_lock, tmp_flags);
+
+		spin_lock_irqsave(&iommu->lock, tmp_flags);
+		clear_bit(domain->id, iommu->domain_ids);
+		iommu->domains[domain->id] = NULL;
+		spin_unlock_irqrestore(&iommu->lock, tmp_flags);
 	}
 
 	spin_unlock_irqrestore(&device_domain_lock, flags);

[PATCH 2/2] intel-iommu: Fix get_domain_for_dev() error path

[Alex Williamson]

If we run out of domain_ids and fail iommu_attach_domain(), we
fall into domain_exit() without having setup enough of the
domain structure for this to do anything useful.  In fact, it
typically runs off into the weeds walking the bogus domain->devices
list.  Just free the domain.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 drivers/pci/intel-iommu.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 8bc56c1..21690a5 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -1835,7 +1835,7 @@ static struct dmar_domain *get_domain_for_dev(struct pci_dev *pdev, int gaw)
 
 	ret = iommu_attach_domain(domain, iommu);
 	if (ret) {
-		domain_exit(domain);
+		free_domain_mem(domain);
 		goto error;
 	}