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Subject[PATCH 5.5 147/151] iommu/vt-d: Ignore devices with out-of-spec domain number
From: Daniel Drake <>

commit da72a379b2ec0bad3eb265787f7008bead0b040c upstream.

VMD subdevices are created with a PCI domain ID of 0x10000 or

These subdevices are also handled like all other PCI devices by

However, when dmar_alloc_pci_notify_info() take records of such devices,
it will truncate the domain ID to a u16 value (in info->seg).
The device at (e.g.) 10000:00:02.0 is then treated by the DMAR code as if
it is 0000:00:02.0.

In the unlucky event that a real device also exists at 0000:00:02.0 and
also has a device-specific entry in the DMAR table,
dmar_insert_dev_scope() will crash on:
  BUG_ON(i >= devices_cnt);

That's basically a sanity check that only one PCI device matches a
single DMAR entry; in this case we seem to have two matching devices.

Fix this by ignoring devices that have a domain number higher than
what can be looked up in the DMAR table.

This problem was carefully diagnosed by Jian-Hong Pan.

Signed-off-by: Lu Baolu <>
Signed-off-by: Daniel Drake <>
Fixes: 59ce0515cdaf3 ("iommu/vt-d: Update DRHD/RMRR/ATSR device scope caches when PCI hotplug happens")
Signed-off-by: Joerg Roedel <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/iommu/dmar.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -28,6 +28,7 @@
#include <linux/slab.h>
#include <linux/iommu.h>
#include <linux/numa.h>
+#include <linux/limits.h>
#include <asm/irq_remapping.h>
#include <asm/iommu_table.h>

@@ -128,6 +129,13 @@ dmar_alloc_pci_notify_info(struct pci_de


+ /*
+ * Ignore devices that have a domain number higher than what can
+ * be looked up in DMAR, e.g. VMD subdevices with domain 0x10000
+ */
+ if (pci_domain_nr(dev->bus) > U16_MAX)
+ return NULL;
/* Only generate path[] for device addition event */
for (tmp = dev; tmp; tmp = tmp->bus->self)

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