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BACKPORT: iommu: Avoid races around device probe

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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>
This commit is contained in:
Robin Murphy
2022-11-04 19:51:43 +00:00
committed by Todd Kjos
parent 60944bdddc
commit 1531e1fb8d
1 changed files with 22 additions and 6 deletions
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28
drivers/iommu/iommu.c
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@@ -201,13 +201,23 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
const struct iommu_ops *ops = dev->bus->iommu_ops; const struct iommu_ops *ops = dev->bus->iommu_ops;
struct iommu_device *iommu_dev; struct iommu_device *iommu_dev;
struct iommu_group *group; struct iommu_group *group;
static DEFINE_MUTEX(iommu_probe_device_lock);
int ret; int ret;
if (!ops) if (!ops)
return -ENODEV; return -ENODEV;
/*
if (!dev_iommu_get(dev)) * Serialise to avoid races between IOMMU drivers registering in
return -ENOMEM; * 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 (!dev_iommu_get(dev)) {
ret = -ENOMEM;
goto err_unlock;
}
if (!try_module_get(ops->owner)) { if (!try_module_get(ops->owner)) {
ret = -EINVAL; ret = -EINVAL;
@@ -227,11 +237,14 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
ret = PTR_ERR(group); ret = PTR_ERR(group);
goto out_release; goto out_release;
} }
iommu_group_put(group);
mutex_lock(&group->mutex);
if (group_list && !group->default_domain && list_empty(&group->entry)) if (group_list && !group->default_domain && list_empty(&group->entry))
list_add_tail(&group->entry, group_list); list_add_tail(&group->entry, group_list);
mutex_unlock(&group->mutex);
iommu_group_put(group);
mutex_unlock(&iommu_probe_device_lock);
iommu_device_link(iommu_dev, dev); iommu_device_link(iommu_dev, dev);
return 0; return 0;
@@ -245,6 +258,9 @@ out_module_put:
err_free: err_free:
dev_iommu_free(dev); dev_iommu_free(dev);
err_unlock:
mutex_unlock(&iommu_probe_device_lock);
return ret; return ret;
} }
@@ -1766,11 +1782,11 @@ int bus_iommu_probe(struct bus_type *bus)
return ret; return ret;
list_for_each_entry_safe(group, next, &group_list, entry) { list_for_each_entry_safe(group, next, &group_list, entry) {
mutex_lock(&group->mutex);
/* Remove item from the list */ /* Remove item from the list */
list_del_init(&group->entry); list_del_init(&group->entry);
mutex_lock(&group->mutex);
/* Try to allocate default domain */ /* Try to allocate default domain */
probe_alloc_default_domain(bus, group); probe_alloc_default_domain(bus, group);