FROMLIST: iommu: Avoid more races around device probe
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
Bug: 313035219
Link: https://lore.kernel.org/all/16f433658661d7cadfea51e7c65da95826112a2b.1700071477.git.robin.murphy@arm.com/
Change-Id: I461df05b03644cb93bc93599cb9f5464bf893923
Signed-off-by: André Draszik <draszik@google.com>
(cherry picked from commit 95307ec5c864e39b7e1ad26eff3e98b06850b4d3)
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index dbfa58e..609d263 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1563,17 +1563,22 @@
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
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index fc7286d..387c5e3 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -301,12 +301,13 @@
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)
@@ -318,10 +319,10 @@
* 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)) {
@@ -350,7 +351,6 @@
mutex_unlock(&group->mutex);
iommu_group_put(group);
- mutex_unlock(&iommu_probe_device_lock);
iommu_device_link(iommu_dev, dev);
return 0;
@@ -365,9 +365,7 @@
err_free:
dev_iommu_free(dev);
-err_unlock:
- mutex_unlock(&iommu_probe_device_lock);
-
+err_out:
return ret;
}
@@ -377,7 +375,9 @@
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;
@@ -1709,7 +1709,9 @@
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;
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 5696314..1fa1db3 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -112,16 +112,20 @@
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);
}
@@ -155,6 +159,8 @@
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.
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 9ff1310..eec008e 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -689,6 +689,7 @@
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);
