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Message-ID: <0952ca36-c5d9-462a-ab7b-b97154c56919@arm.com>
Date: Thu, 7 Nov 2024 15:01:50 +0000
From: Robin Murphy <robin.murphy@....com>
To: Will Deacon <will@...nel.org>, Pratyush Brahma <quic_pbrahma@...cinc.com>
Cc: catalin.marinas@....com, kernel-team@...roid.com, joro@...tes.org,
jgg@...pe.ca, jsnitsel@...hat.com, robdclark@...omium.org,
quic_c_gdjako@...cinc.com, dmitry.baryshkov@...aro.org,
linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
linux-kernel@...r.kernel.org, quic_charante@...cinc.com,
stable@...r.kernel.org, Prakash Gupta <quic_guptap@...cinc.com>
Subject: Re: [PATCH v2] iommu/arm-smmu: Defer probe of clients after smmu
device bound
On 29/10/2024 4:15 pm, Will Deacon wrote:
> On Fri, 04 Oct 2024 14:34:28 +0530, Pratyush Brahma wrote:
>> Null pointer dereference occurs due to a race between smmu
>> driver probe and client driver probe, when of_dma_configure()
>> for client is called after the iommu_device_register() for smmu driver
>> probe has executed but before the driver_bound() for smmu driver
>> has been called.
>>
>> Following is how the race occurs:
>>
>> [...]
>
> Applied to will (for-joerg/arm-smmu/updates), thanks!
>
> [1/1] iommu/arm-smmu: Defer probe of clients after smmu device bound
> https://git.kernel.org/will/c/229e6ee43d2a
I've finally got to the point of proving to myself that this isn't the
right fix, since once we do get __iommu_probe_device() working properly
in the correct order, iommu_device_register() then runs into the same
condition itself. Diff below should make this issue go away - I'll write
up proper patches once I've tested it a little more.
Thanks,
Robin.
----->8-----
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 737c5b882355..b7dcb1494aa4 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3171,8 +3171,8 @@ static struct platform_driver arm_smmu_driver;
static
struct arm_smmu_device *arm_smmu_get_by_fwnode(struct fwnode_handle *fwnode)
{
- struct device *dev = driver_find_device_by_fwnode(&arm_smmu_driver.driver,
- fwnode);
+ struct device *dev = bus_find_device_by_fwnode(&platform_bus_type, fwnode);
+
put_device(dev);
return dev ? dev_get_drvdata(dev) : NULL;
}
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 8321962b3714..aba315aa6848 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1411,8 +1411,8 @@ static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap)
static
struct arm_smmu_device *arm_smmu_get_by_fwnode(struct fwnode_handle *fwnode)
{
- struct device *dev = driver_find_device_by_fwnode(&arm_smmu_driver.driver,
- fwnode);
+ struct device *dev = bus_find_device_by_fwnode(&platform_bus_type, fwnode);
+
put_device(dev);
return dev ? dev_get_drvdata(dev) : NULL;
}
@@ -2232,21 +2232,6 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
i, irq);
}
- err = iommu_device_sysfs_add(&smmu->iommu, smmu->dev, NULL,
- "smmu.%pa", &smmu->ioaddr);
- if (err) {
- dev_err(dev, "Failed to register iommu in sysfs\n");
- return err;
- }
-
- err = iommu_device_register(&smmu->iommu, &arm_smmu_ops,
- using_legacy_binding ? NULL : dev);
- if (err) {
- dev_err(dev, "Failed to register iommu\n");
- iommu_device_sysfs_remove(&smmu->iommu);
- return err;
- }
-
platform_set_drvdata(pdev, smmu);
/* Check for RMRs and install bypass SMRs if any */
@@ -2255,6 +2240,18 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
arm_smmu_device_reset(smmu);
arm_smmu_test_smr_masks(smmu);
+ err = iommu_device_sysfs_add(&smmu->iommu, smmu->dev, NULL,
+ "smmu.%pa", &smmu->ioaddr);
+ if (err)
+ return dev_err_probe(dev, err, "Failed to register iommu in sysfs\n");
+
+ err = iommu_device_register(&smmu->iommu, &arm_smmu_ops,
+ using_legacy_binding ? NULL : dev);
+ if (err) {
+ iommu_device_sysfs_remove(&smmu->iommu);
+ return dev_err_probe(dev, err, "Failed to register iommu\n");
+ }
+
/*
* We want to avoid touching dev->power.lock in fastpaths unless
* it's really going to do something useful - pm_runtime_enabled()
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