Commit 2490e55f authored Nov 04, 2022 by Robin Murphy Committed by Srinivasarao Pathipati Feb 15, 2023

BACKPORT: iommu: Avoid races around device probe

We currently have 3 different ways that __iommu_probe_device() may be
called, but no real guarantee that multiple callers can't tread on each
other, especially once asynchronous driver probe gets involved. It would
likely have taken a fair bit of luck to hit this previously, but commit
57365a04c921 ("iommu: Move bus setup to IOMMU device registration") ups
the odds since now it's not just omap-iommu that may trigger multiple
bus_iommu_probe() calls in parallel if probing asynchronously.

Add a lock to ensure we can't try to double-probe a device, and also
close some possible race windows to make sure we're truly robust against
trying to double-initialise a group via two different member devices.

Reported-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Brian Norris <briannorris@chromium.org>
Fixes: 57365a04c921 ("iommu: Move bus setup to IOMMU device registration")
Link: https://lore.kernel.org/r/1946ef9f774851732eed78760a78ec40dbc6d178.1667591503.git.robin.murphy@arm.com

Signed-off-by: Joerg Roedel <jroedel@suse.de>

Bug: 269232600
(cherry picked from commit 01657bc14a3990c665375f77978631fee77b1fce)
Change-Id: Ie87f8f7a7b90431c3a2682923961885ce7b239f3
Signed-off-by: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Signed-off-by: Srinivasarao Pathipati <quic_spathi@quicinc.com>

parent 3daec397

drivers/iommu/iommu.c

+18 −2

Original line number	Diff line number	Diff line
		@@ -177,14 +177,25 @@ static void iommu_free_dev_param(struct device *dev)
		int iommu_probe_device(struct device *dev)
		{
		const struct iommu_ops *ops = dev->bus->iommu_ops;
		static DEFINE_MUTEX(iommu_probe_device_lock);
		int ret;

		WARN_ON(dev->iommu_group);
		if (!ops)
		return -EINVAL;

		if (!iommu_get_dev_param(dev))
		return -ENOMEM;
		/*
		* Serialise to avoid races between IOMMU drivers registering in
		* parallel and/or the "replay" calls from ACPI/OF code via client
		* driver probe. Once the latter have been cleaned up we should
		* probably be able to use device_lock() here to minimise the scope,
		* but for now enforcing a simple global ordering is fine.
		*/
		mutex_lock(&iommu_probe_device_lock);
		if (!iommu_get_dev_param(dev)) {
		ret = -ENOMEM;
		goto err_unlock;
		}

		if (!try_module_get(ops->owner)) {
		ret = -EINVAL;
		@@ -195,12 +206,17 @@ int iommu_probe_device(struct device *dev)
		if (ret)
		goto err_module_put;

		mutex_unlock(&iommu_probe_device_lock);

		return 0;

		err_module_put:
		module_put(ops->owner);
		err_free_dev_param:
		iommu_free_dev_param(dev);
		err_unlock:
		mutex_unlock(&iommu_probe_device_lock);

		return ret;
		}