linux-kernel - [PATCH AUTOSEL 6.0 07/32] iommu/vt-d: Handle race between registration and device probe

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Message-Id: <20221018000729.2730519-7-sashal@kernel.org>
Date:   Mon, 17 Oct 2022 20:07:04 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.com>,
        Joerg Roedel <jroedel@...e.de>,
        Sasha Levin <sashal@...nel.org>, dwmw2@...radead.org,
        baolu.lu@...ux.intel.com, joro@...tes.org, will@...nel.org,
        iommu@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.0 07/32] iommu/vt-d: Handle race between registration and device probe

From: Robin Murphy <robin.murphy@....com>

[ Upstream commit c919739ce4721ecf7b96b99253b032df30fcf19b ]

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, and a more in-depth rework of this locking
is underway, so no attempt is made to address it here.

Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Signed-off-by: Robin Murphy <robin.murphy@....com>
Link: https://lore.kernel.org/r/579f2692291bcbfc3ac64f7456fcff0d629af131.1660572783.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 31bc50e538a3..ed63386b9b60 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4457,7 +4457,7 @@ 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);
-- 
2.35.1