[PATCH 4.4 095/101] iommu: Handle default domain attach failure

Greg Kroah-Hartman
2017-07-03T13:40:48Z

From: Robin Murphy <robin.murphy@arm.com>

commit 797a8b4d768c58caac58ee3e8cb36a164d1b7751 upstream.

We wouldn't normally expect ops->attach_dev() to fail, but on IOMMUs
with limited hardware resources, or generally misconfigured systems,
it is certainly possible. We report failure correctly from the external
iommu_attach_device() interface, but do not do so in iommu_group_add()
when attaching to the default domain. The result of failure there is
that the device, group and domain all get left in a broken,
part-configured state which leads to weird errors and misbehaviour down
the line when IOMMU API calls sort-of-but-don't-quite work.

Check the return value of __iommu_attach_device() on the default domain,
and refactor the error handling paths to cope with its failure and clean
up correctly in such cases.

Fixes: e39cb8a3aa98 ("iommu: Make sure a device is always attached to a domain")
Reported-by: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/iommu/iommu.c | 37 ++++++++++++++++++++++++-------------
1 file changed, 24 insertions(+), 13 deletions(-)

--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -391,36 +391,30 @@ int iommu_group_add_device(struct iommu_
device->dev = dev;

ret = sysfs_create_link(&dev->kobj, &group->kobj, "iommu_group");
- if (ret) {
- kfree(device);
- return ret;
- }
+ if (ret)
+ goto err_free_device;

device->name = kasprintf(GFP_KERNEL, "%s", kobject_name(&dev->kobj));
rename:
if (!device->name) {
- sysfs_remove_link(&dev->kobj, "iommu_group");
- kfree(device);
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto err_remove_link;
}

ret = sysfs_create_link_nowarn(group->devices_kobj,
&dev->kobj, device->name);
if (ret) {
- kfree(device->name);
if (ret == -EEXIST && i >= 0) {
/*
* Account for the slim chance of collision
* and append an instance to the name.
*/
+ kfree(device->name);
device->name = kasprintf(GFP_KERNEL, "%s.%d",
kobject_name(&dev->kobj), i++);
goto rename;
}
-
- sysfs_remove_link(&dev->kobj, "iommu_group");
- kfree(device);
- return ret;
+ goto err_free_name;
}

kobject_get(group->devices_kobj);
@@ -432,8 +426,10 @@ rename:
mutex_lock(&group->mutex);
list_add_tail(&device->list, &group->devices);
if (group->domain)
- __iommu_attach_device(group->domain, dev);
+ ret = __iommu_attach_device(group->domain, dev);
mutex_unlock(&group->mutex);
+ if (ret)
+ goto err_put_group;

/* Notify any listeners about change to group. */
blocking_notifier_call_chain(&group->notifier,
@@ -444,6 +440,21 @@ rename:
pr_info("Adding device %s to group %d\n", dev_name(dev), group->id);

return 0;
+
+err_put_group:
+ mutex_lock(&group->mutex);
+ list_del(&device->list);
+ mutex_unlock(&group->mutex);
+ dev->iommu_group = NULL;
+ kobject_put(group->devices_kobj);
+err_free_name:
+ kfree(device->name);
+err_remove_link:
+ sysfs_remove_link(&dev->kobj, "iommu_group");
+err_free_device:
+ kfree(device);
+ pr_err("Failed to add device %s to group %d: %d\n", dev_name(dev), group->id, ret);
+ return ret;
}
EXPORT_SYMBOL_GPL(iommu_group_add_device);