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FROMLIST: iommu: Avoid more races around device probe

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It turns out there are more subtle races beyond just the main part of
__iommu_probe_device() itself running in parallel - the dev_iommu_free()
on the way out of an unsuccessful probe can still manage to trip up
concurrent accesses to a device's fwspec. Thus, extend the scope of
iommu_probe_device_lock() to also serialise fwspec creation and initial
retrieval.

Reported-by: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Link: https://lore.kernel.org/linux-iommu/e2e20e1c-6450-4ac5-9804-b0000acdf7de@quicinc.com/
Fixes: 01657bc14a39 ("iommu: Avoid races around device probe")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Bug: 308940593
Link: https://lore.kernel.org/all/16f433658661d7cadfea51e7c65da95826112a2b.1700071477.git.robin.murphy@arm.com/
Change-Id: I461df05b03644cb93bc93599cb9f5464bf893923
Signed-off-by: André Draszik <draszik@google.com>
This commit is contained in:
Robin Murphy 2023-11-15 18:25:44 +00:00 committed by Treehugger Robot
parent 5c8e593916
commit 95307ec5c8
4 changed files with 25 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/acpi/scan.c
View File

@ -1563,17 +1563,22 @@ static const struct iommu_ops *acpi_iommu_configure_id(struct device *dev,
int err;
const struct iommu_ops *ops;
/* Serialise to make dev->iommu stable under our potential fwspec */
mutex_lock(&iommu_probe_device_lock);
/*
* If we already translated the fwspec there is nothing left to do,
* return the iommu_ops.
*/
ops = acpi_iommu_fwspec_ops(dev);
if (ops)
if (ops) {
mutex_unlock(&iommu_probe_device_lock);
return ops;
}
err = iort_iommu_configure_id(dev, id_in);
if (err && err != -EPROBE_DEFER)
err = viot_iommu_configure(dev);
mutex_unlock(&iommu_probe_device_lock);
/*
* If we have reason to believe the IOMMU driver missed the initial

16
drivers/iommu/iommu.c
View File

@ -308,12 +308,13 @@ static u32 dev_iommu_get_max_pasids(struct device *dev)
return min_t(u32, max_pasids, dev->iommu->iommu_dev->max_pasids);
}
DEFINE_MUTEX(iommu_probe_device_lock);
static int __iommu_probe_device(struct device *dev, struct list_head *group_list)
{
const struct iommu_ops *ops = dev->bus->iommu_ops;
struct iommu_device *iommu_dev;
struct iommu_group *group;
static DEFINE_MUTEX(iommu_probe_device_lock);
int ret;
if (!ops)
@ -325,10 +326,10 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
* 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);
lockdep_assert_held(&iommu_probe_device_lock);
if (!dev_iommu_get(dev)) {
ret = -ENOMEM;
goto err_unlock;
goto err_out;
}
if (!try_module_get(ops->owner)) {
@ -357,7 +358,6 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
mutex_unlock(&group->mutex);
iommu_group_put(group);
mutex_unlock(&iommu_probe_device_lock);
iommu_device_link(iommu_dev, dev);
return 0;
@ -372,9 +372,7 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
err_free:
dev_iommu_free(dev);
err_unlock:
mutex_unlock(&iommu_probe_device_lock);
err_out:
return ret;
}
@ -384,7 +382,9 @@ int iommu_probe_device(struct device *dev)
struct iommu_group *group;
int ret;
mutex_lock(&iommu_probe_device_lock);
ret = __iommu_probe_device(dev, NULL);
mutex_unlock(&iommu_probe_device_lock);
if (ret)
goto err_out;
@ -1716,7 +1716,9 @@ static int probe_iommu_group(struct device *dev, void *data)
return 0;
}
mutex_lock(&iommu_probe_device_lock);
ret = __iommu_probe_device(dev, group_list);
mutex_unlock(&iommu_probe_device_lock);
if (ret == -ENODEV)
ret = 0;

12
drivers/iommu/of_iommu.c
View File

@ -113,16 +113,20 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
const u32 *id)
{
const struct iommu_ops *ops = NULL;
struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
struct iommu_fwspec *fwspec;
int err = NO_IOMMU;
if (!master_np)
return NULL;
/* Serialise to make dev->iommu stable under our potential fwspec */
mutex_lock(&iommu_probe_device_lock);
fwspec = dev_iommu_fwspec_get(dev);
if (fwspec) {
if (fwspec->ops)
if (fwspec->ops) {
mutex_unlock(&iommu_probe_device_lock);
return fwspec->ops;
}
/* In the deferred case, start again from scratch */
iommu_fwspec_free(dev);
}
@ -156,6 +160,8 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
fwspec = dev_iommu_fwspec_get(dev);
ops = fwspec->ops;
}
mutex_unlock(&iommu_probe_device_lock);
/*
* If we have reason to believe the IOMMU driver missed the initial
* probe for dev, replay it to get things in order.

1
include/linux/iommu.h
View File

@ -689,6 +689,7 @@ static inline void dev_iommu_priv_set(struct device *dev, void *priv)
dev->iommu->priv = priv;
}
extern struct mutex iommu_probe_device_lock;
int iommu_probe_device(struct device *dev);
void iommu_release_device(struct device *dev);