[PATCH 2/2] iommu/sva: Remove mm parameter from SVA bind API

Jacob Pan
2021-04-09T01:43:05Z

The mm parameter in iommu_sva_bind_device() is intended for privileged
process perform bind() on behalf of other processes. This use case has
yet to be materialized, let alone potential security implications of
adding kernel hooks without explicit user consent.
In addition, with the agreement that IOASID allocation shall be subject
cgroup limit. It will be inline with misc cgroup proposal if IOASID
allocation as part of the SVA bind is limited to the current task.

Link: https://lore.kernel.org/linux-iommu/20210303160205.151d114e@jacob-builder/
Link: https://lore.kernel.org/linux-iommu/YFhiMLR35WWMW%2FHu@myrica/
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
drivers/dma/idxd/cdev.c | 2 +-
drivers/dma/idxd/init.c | 2 +-
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 6 ++---
drivers/iommu/iommu-sva-lib.c | 30 +++++++++++++++++++------
drivers/iommu/iommu-sva-lib.h | 4 ++--
drivers/iommu/iommu.c | 16 ++++++++-----
drivers/misc/uacce/uacce.c | 2 +-
include/linux/iommu.h | 7 +++---
8 files changed, 45 insertions(+), 24 deletions(-)

diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
index 21ec82b..8c3347c 100644
--- a/drivers/dma/idxd/cdev.c
+++ b/drivers/dma/idxd/cdev.c
@@ -103,7 +103,7 @@ static int idxd_cdev_open(struct inode *inode, struct file *filp)
filp->private_data = ctx;

if (device_pasid_enabled(idxd)) {
- sva = iommu_sva_bind_device(dev, current->mm, 0);
+ sva = iommu_sva_bind_device(dev, 0);
if (IS_ERR(sva)) {
rc = PTR_ERR(sva);
dev_err(dev, "pasid allocation failed: %d\n", rc);
diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index cdc85f1..a583f79 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -306,7 +306,7 @@ static int idxd_enable_system_pasid(struct idxd_device *idxd)

flags = IOMMU_SVA_BIND_SUPERVISOR;

- sva = iommu_sva_bind_device(&idxd->pdev->dev, NULL, flags);
+ sva = iommu_sva_bind_device(&idxd->pdev->dev, flags);
if (IS_ERR(sva)) {
dev_warn(&idxd->pdev->dev,
"iommu sva bind failed: %ld\n", PTR_ERR(sva));
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
index 23e287e..bdd5c79 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -329,7 +329,7 @@ __arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm)
return ERR_PTR(-ENOMEM);

/* Allocate a PASID for this mm if necessary */
- ret = iommu_sva_alloc_pasid(mm, 1, (1U << master->ssid_bits) - 1);
+ ret = iommu_sva_alloc_pasid(1, (1U << master->ssid_bits) - 1);
if (ret)
goto err_free_bond;

@@ -347,7 +347,7 @@ __arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm)
return &bond->sva;

err_free_pasid:
- iommu_sva_free_pasid(mm);
+ iommu_sva_free_pasid();
err_free_bond:
kfree(bond);
return ERR_PTR(ret);
@@ -377,7 +377,7 @@ void arm_smmu_sva_unbind(struct iommu_sva *handle)
if (refcount_dec_and_test(&bond->refs)) {
list_del(&bond->list);
arm_smmu_mmu_notifier_put(bond->smmu_mn);
- iommu_sva_free_pasid(bond->mm);
+ iommu_sva_free_pasid();
kfree(bond);
}
mutex_unlock(&sva_lock);
diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
index bd41405..bd99f6b 100644
--- a/drivers/iommu/iommu-sva-lib.c
+++ b/drivers/iommu/iommu-sva-lib.c
@@ -12,27 +12,33 @@ static DECLARE_IOASID_SET(iommu_sva_pasid);

/**
* iommu_sva_alloc_pasid - Allocate a PASID for the mm
- * @mm: the mm
* @min: minimum PASID value (inclusive)
* @max: maximum PASID value (inclusive)
*
- * Try to allocate a PASID for this mm, or take a reference to the existing one
- * provided it fits within the [@min, @max] range. On success the PASID is
- * available in mm->pasid, and must be released with iommu_sva_free_pasid().
+ * Try to allocate a PASID for the current mm, or take a reference to the
+ * existing one provided it fits within the [@min, @max] range. On success
+ * the PASID is available in the current mm->pasid, and must be released with
+ * iommu_sva_free_pasid().
* @min must be greater than 0, because 0 indicates an unused mm->pasid.
*
* Returns 0 on success and < 0 on error.
*/
-int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
+int iommu_sva_alloc_pasid(ioasid_t min, ioasid_t max)
{
int ret = 0;
ioasid_t pasid;
+ struct mm_struct *mm;

if (min == INVALID_IOASID || max == INVALID_IOASID ||
min == 0 || max < min)
return -EINVAL;

mutex_lock(&iommu_sva_lock);
+ mm = get_task_mm(current);
+ if (!mm) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
if (mm->pasid) {
if (mm->pasid >= min && mm->pasid <= max)
ioasid_get(mm->pasid);
@@ -45,22 +51,32 @@ int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
else
mm->pasid = pasid;
}
+ mmput(mm);
+out_unlock:
mutex_unlock(&iommu_sva_lock);
return ret;
}
EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);

/**
- * iommu_sva_free_pasid - Release the mm's PASID
+ * iommu_sva_free_pasid - Release the current mm's PASID
* @mm: the mm
*
* Drop one reference to a PASID allocated with iommu_sva_alloc_pasid()
*/
-void iommu_sva_free_pasid(struct mm_struct *mm)
+void iommu_sva_free_pasid(void)
{
+ struct mm_struct *mm;
+
mutex_lock(&iommu_sva_lock);
+ mm = get_task_mm(current);
+ if (!mm)
+ goto out_unlock;
+
if (ioasid_put(mm->pasid))
mm->pasid = 0;
+ mmput(mm);
+out_unlock:
mutex_unlock(&iommu_sva_lock);
}
EXPORT_SYMBOL_GPL(iommu_sva_free_pasid);
diff --git a/drivers/iommu/iommu-sva-lib.h b/drivers/iommu/iommu-sva-lib.h
index b40990a..278b8b4 100644
--- a/drivers/iommu/iommu-sva-lib.h
+++ b/drivers/iommu/iommu-sva-lib.h
@@ -8,8 +8,8 @@
#include <linux/ioasid.h>
#include <linux/mm_types.h>

-int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max);
-void iommu_sva_free_pasid(struct mm_struct *mm);
+int iommu_sva_alloc_pasid(ioasid_t min, ioasid_t max);
+void iommu_sva_free_pasid(void);
struct mm_struct *iommu_sva_find(ioasid_t pasid);

#endif /* _IOMMU_SVA_LIB_H */
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index bf0a20f..25840e6 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -23,6 +23,7 @@
#include <linux/property.h>
#include <linux/fsl/mc.h>
#include <linux/module.h>
+#include <linux/sched/mm.h>
#include <trace/events/iommu.h>

static struct kset *iommu_group_kset;
@@ -2959,9 +2960,8 @@ int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);

/**
- * iommu_sva_bind_device() - Bind a process address space to a device
+ * iommu_sva_bind_device() - Bind the current process address space to a device
* @dev: the device
- * @mm: the mm to bind, caller must hold a reference to it
* @flags: options for the bind operation
*
* Create a bond between device and address space, allowing the device to access
@@ -2975,9 +2975,10 @@ EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
* On error, returns an ERR_PTR value.
*/
struct iommu_sva *
-iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, unsigned int flags)
+iommu_sva_bind_device(struct device *dev, unsigned int flags)
{
struct iommu_group *group;
+ struct mm_struct *mm = NULL;
struct iommu_sva *handle = ERR_PTR(-EINVAL);
const struct iommu_ops *ops = dev->bus->iommu_ops;

@@ -2989,8 +2990,11 @@ iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, unsigned int fla
return ERR_PTR(-ENODEV);

/* Supervisor SVA does not need the current mm */
- if ((flags & IOMMU_SVA_BIND_SUPERVISOR) && mm)
- return ERR_PTR(-EINVAL);
+ if (!(flags & IOMMU_SVA_BIND_SUPERVISOR)) {
+ mm = get_task_mm(current);
+ if (!mm)
+ return ERR_PTR(-EINVAL);
+ }
/* Ensure device count and domain don't change while we're binding */
mutex_lock(&group->mutex);

@@ -3004,6 +3008,8 @@ iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, unsigned int fla
goto out_unlock;

handle = ops->sva_bind(dev, mm, flags);
+ if (mm)
+ mmput(mm);
out_unlock:
mutex_unlock(&group->mutex);
iommu_group_put(group);
diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
index 27e0e04..da4401a 100644
--- a/drivers/misc/uacce/uacce.c
+++ b/drivers/misc/uacce/uacce.c
@@ -99,7 +99,7 @@ static int uacce_bind_queue(struct uacce_device *uacce, struct uacce_queue *q)
if (!(uacce->flags & UACCE_DEV_SVA))
return 0;

- handle = iommu_sva_bind_device(uacce->parent, current->mm, 0);
+ handle = iommu_sva_bind_device(uacce->parent, 0);
if (IS_ERR(handle))
return PTR_ERR(handle);

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index a3fbaa2..cf752f3 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -231,8 +231,8 @@ struct iommu_iotlb_gather {
* @dev_feat_enabled: check enabled feature
* @aux_attach/detach_dev: aux-domain specific attach/detach entries.
* @aux_get_pasid: get the pasid given an aux-domain
- * @sva_bind: Bind process address space to device
- * @sva_unbind: Unbind process address space from device
+ * @sva_bind: Bind the current process address space to device
+ * @sva_unbind: Unbind the current process address space from device
* @sva_get_pasid: Get PASID associated to a SVA handle
* @page_response: handle page request response
* @cache_invalidate: invalidate translation caches
@@ -652,7 +652,6 @@ void iommu_aux_detach_device(struct iommu_domain *domain, struct device *dev);
int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev);

struct iommu_sva *iommu_sva_bind_device(struct device *dev,
- struct mm_struct *mm,
unsigned int flags);
void iommu_sva_unbind_device(struct iommu_sva *handle);
u32 iommu_sva_get_pasid(struct iommu_sva *handle);
@@ -1028,7 +1027,7 @@ iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
}

static inline struct iommu_sva *
-iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, unsigned int flags)
+iommu_sva_bind_device(struct device *dev, unsigned int flags)
{
return NULL;
}
--
2.7.4