This is a note to let you know that I've just added the patch titled iommu: Avoid races around device probe to the 6.1-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: iommu-avoid-races-around-device-probe.patch and it can be found in the queue-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit f817e17545a6de6f4717a6d59a42a0731973711e Author: Robin Murphy <robin.murphy@xxxxxxx> Date: Fri Nov 4 19:51:43 2022 +0000 iommu: Avoid races around device probe [ Upstream commit 01657bc14a3990c665375f77978631fee77b1fce ] 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@xxxxxxxxxxxx> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx> Tested-by: Brian Norris <briannorris@xxxxxxxxxxxx> Fixes: 57365a04c921 ("iommu: Move bus setup to IOMMU device registration") Link: https://lore.kernel.org/r/1946ef9f774851732eed78760a78ec40dbc6d178.1667591503.git.robin.murphy@xxxxxxx Signed-off-by: Joerg Roedel <jroedel@xxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 65a3b3d886dc..959d895fc1df 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -283,13 +283,23 @@ 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) return -ENODEV; - - if (!dev_iommu_get(dev)) - return -ENOMEM; + /* + * Serialise to avoid races between IOMMU drivers registering in + * 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)) { ret = -EINVAL; @@ -309,11 +319,14 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list ret = PTR_ERR(group); goto out_release; } - iommu_group_put(group); + mutex_lock(&group->mutex); if (group_list && !group->default_domain && list_empty(&group->entry)) 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); return 0; @@ -328,6 +341,9 @@ 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); + return ret; } @@ -1799,11 +1815,11 @@ int bus_iommu_probe(struct bus_type *bus) return ret; list_for_each_entry_safe(group, next, &group_list, entry) { + mutex_lock(&group->mutex); + /* Remove item from the list */ list_del_init(&group->entry); - mutex_lock(&group->mutex); - /* Try to allocate default domain */ probe_alloc_default_domain(bus, group);