linux-kernel - [PATCH AUTOSEL 5.4 71/73] iommu/vt-d: Ignore devices with out-of-spec domain number

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Message-Id: <20200318205337.16279-71-sashal@kernel.org>
Date:   Wed, 18 Mar 2020 16:53:35 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Daniel Drake <drake@...lessm.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>,
        Sasha Levin <sashal@...nel.org>,
        iommu@...ts.linux-foundation.org
Subject: [PATCH AUTOSEL 5.4 71/73] iommu/vt-d: Ignore devices with out-of-spec domain number

From: Daniel Drake <drake@...lessm.com>

[ Upstream commit da72a379b2ec0bad3eb265787f7008bead0b040c ]

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

These subdevices are also handled like all other PCI devices by
dmar_pci_bus_notifier().

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 <baolu.lu@...ux.intel.com>
Signed-off-by: Daniel Drake <drake@...lessm.com>
Fixes: 59ce0515cdaf3 ("iommu/vt-d: Update DRHD/RMRR/ATSR device scope caches when PCI hotplug happens")
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iommu/dmar.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index aa15155b9401f..34e705d3b6bb6 100644
--- 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_dev *dev, unsigned long event)
 
 	BUG_ON(dev->is_virtfn);
 
+	/*
+	 * 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 */
 	if (event == BUS_NOTIFY_ADD_DEVICE)
 		for (tmp = dev; tmp; tmp = tmp->bus->self)
-- 
2.20.1