linux-kernel - [PATCH v3 01/15] iommu/vt-d: Handle race between registration and device probe

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Message-Id: <894db0ccae854b35c73814485569b634237b5538.1657034828.git.robin.murphy@arm.com>
Date:   Tue,  5 Jul 2022 18:08:24 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     joro@...tes.org
Cc:     will@...nel.org, iommu@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, baolu.lu@...ux.intel.com,
        suravee.suthikulpanit@....com, vasant.hegde@....com,
        mjrosato@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        schnelle@...ux.ibm.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 01/15] iommu/vt-d: Handle race between registration and device probe

Currently we rely on registering all our instances before initially
allowing any .probe_device calls via bus_set_iommu(). In preparation for
phasing out the latter, make sure we won't inadvertently return success
for a device associated with a known but not yet registered instance,
otherwise we'll run straight into iommu_group_get_for_dev() trying to
use NULL ops.

That also highlights an issue with intel_iommu_get_resv_regions() taking
dmar_global_lock from within a section where intel_iommu_init() already
holds it, which already exists via probe_acpi_namespace_devices() when
an ANDD device is probed, but gets more obvious with the upcoming change
to iommu_device_register(). Since they are both read locks it manages
not to deadlock in practice, so I'm leaving it here for someone with
more confidence to tackle a larger rework of the locking.

Signed-off-by: Robin Murphy <robin.murphy@....com>
---

v3: New

 drivers/iommu/intel/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 44016594831d..3e02c08802a0 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4600,7 +4600,7 @@ static struct iommu_device *intel_iommu_probe_device(struct device *dev)
 	u8 bus, devfn;

 	iommu = device_to_iommu(dev, &bus, &devfn);
-	if (!iommu)
+	if (!iommu || !iommu->iommu.ops)
 		return ERR_PTR(-ENODEV);

 	info = kzalloc(sizeof(*info), GFP_KERNEL);
-- 
2.36.1.dirty