6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Robin Murphy robin.murphy@arm.com
commit a2e7e59a94269484a83386972ca07c22fd188854 upstream.
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@qui... Fixes: 01657bc14a39 ("iommu: Avoid races around device probe") Signed-off-by: Robin Murphy robin.murphy@arm.com Acked-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Reviewed-by: André Draszik andre.draszik@linaro.org Tested-by: André Draszik andre.draszik@linaro.org Link: https://lore.kernel.org/r/16f433658661d7cadfea51e7c65da95826112a2b.170007147... Cc: stable@vger.kernel.org Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/acpi/scan.c | 7 ++++++- drivers/iommu/iommu.c | 19 +++++++++---------- drivers/iommu/of_iommu.c | 12 +++++++++--- include/linux/iommu.h | 1 + 4 files changed, 25 insertions(+), 14 deletions(-)
--- a/drivers/acpi/scan.c +++ b/drivers/acpi/scan.c @@ -1563,17 +1563,22 @@ static const struct iommu_ops *acpi_iomm 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 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -278,12 +278,13 @@ static void dev_iommu_free(struct device kfree(param); }
+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) @@ -295,11 +296,9 @@ static int __iommu_probe_device(struct d * 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; - } + lockdep_assert_held(&iommu_probe_device_lock); + if (!dev_iommu_get(dev)) + return -ENOMEM;
if (!try_module_get(ops->owner)) { ret = -EINVAL; @@ -326,7 +325,6 @@ static int __iommu_probe_device(struct d mutex_unlock(&group->mutex); iommu_group_put(group);
- mutex_unlock(&iommu_probe_device_lock); iommu_device_link(iommu_dev, dev);
return 0; @@ -341,9 +339,6 @@ out_module_put: err_free: dev_iommu_free(dev);
-err_unlock: - mutex_unlock(&iommu_probe_device_lock); - return ret; }
@@ -353,7 +348,9 @@ int iommu_probe_device(struct device *de 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;
@@ -1684,7 +1681,9 @@ static int probe_iommu_group(struct devi 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;
--- a/drivers/iommu/of_iommu.c +++ b/drivers/iommu/of_iommu.c @@ -112,16 +112,20 @@ const struct iommu_ops *of_iommu_configu 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 @@ const struct iommu_ops *of_iommu_configu 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. --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -657,6 +657,7 @@ static inline void dev_iommu_priv_set(st 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);