From 01657bc14a3990c665375f77978631fee77b1fce Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Fri, 4 Nov 2022 19:51:43 +0000 Subject: [PATCH] iommu: Avoid races around device probe 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 Signed-off-by: Robin Murphy Tested-by: Brian Norris 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 --- drivers/iommu/iommu.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 6ca377f4fbf9e..7c99d8eb3182a 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -306,13 +306,23 @@ 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; @@ -333,11 +343,14 @@ 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; @@ -352,6 +365,9 @@ 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; } @@ -1824,11 +1840,11 @@ 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);