[PATCH v2 7/7] vfio: Remove calls to vfio_group_add_container_user()

Jason Gunthorpe
2022-04-21T16:31:06Z

When the open_device() op is called the container_users is incremented and
held incremented until close_device(). Thus, so long as drivers call
functions within their open_device()/close_device() region they do not
need to worry about the container_users.

These functions can all only be called between open_device() and
close_device():

vfio_pin_pages()
vfio_unpin_pages()
vfio_dma_rw()
vfio_register_notifier()
vfio_unregister_notifier()

Eliminate the calls to vfio_group_add_container_user() and add
vfio_assert_device_open() to detect driver mis-use.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/vfio/vfio.c | 78 +++++++++------------------------------------
1 file changed, 15 insertions(+), 63 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index ba6fae95555ec7..b566ae3d320b36 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1330,6 +1330,12 @@ static int vfio_group_add_container_user(struct vfio_group *group)

static const struct file_operations vfio_device_fops;

+/* true if the vfio_device has open_device() called but not close_device() */
+static bool vfio_assert_device_open(struct vfio_device *device)
+{
+ return !WARN_ON_ONCE(!READ_ONCE(device->open_count));
+}
+
static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
{
struct vfio_device *device;
@@ -1544,8 +1550,10 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
struct vfio_device *device = filep->private_data;

mutex_lock(&device->dev_set->lock);
- if (!--device->open_count && device->ops->close_device)
+ vfio_assert_device_open(device);
+ if (device->open_count == 1 && device->ops->close_device)
device->ops->close_device(device);
+ device->open_count--;
mutex_unlock(&device->dev_set->lock);

module_put(device->dev->driver->owner);
@@ -2112,7 +2120,7 @@ int vfio_pin_pages(struct vfio_device *vdev, unsigned long *user_pfn, int npage,
struct vfio_iommu_driver *driver;
int ret;

- if (!user_pfn || !phys_pfn || !npage)
+ if (!user_pfn || !phys_pfn || !npage || !vfio_assert_device_open(vdev))
return -EINVAL;

if (npage > VFIO_PIN_PAGES_MAX_ENTRIES)
@@ -2121,10 +2129,6 @@ int vfio_pin_pages(struct vfio_device *vdev, unsigned long *user_pfn, int npage,
if (group->dev_counter > 1)
return -EINVAL;

- ret = vfio_group_add_container_user(group);
- if (ret)
- return ret;
-
container = group->container;
driver = container->iommu_driver;
if (likely(driver && driver->ops->pin_pages))
@@ -2134,8 +2138,6 @@ int vfio_pin_pages(struct vfio_device *vdev, unsigned long *user_pfn, int npage,
else
ret = -ENOTTY;

- vfio_group_try_dissolve_container(group);
-
return ret;
}
EXPORT_SYMBOL(vfio_pin_pages);
@@ -2156,16 +2158,12 @@ int vfio_unpin_pages(struct vfio_device *vdev, unsigned long *user_pfn,
struct vfio_iommu_driver *driver;
int ret;

- if (!user_pfn || !npage)
+ if (!user_pfn || !npage || !vfio_assert_device_open(vdev))
return -EINVAL;

if (npage > VFIO_PIN_PAGES_MAX_ENTRIES)
return -E2BIG;

- ret = vfio_group_add_container_user(vdev->group);
- if (ret)
- return ret;
-
container = vdev->group->container;
driver = container->iommu_driver;
if (likely(driver && driver->ops->unpin_pages))
@@ -2174,8 +2172,6 @@ int vfio_unpin_pages(struct vfio_device *vdev, unsigned long *user_pfn,
else
ret = -ENOTTY;

- vfio_group_try_dissolve_container(vdev->group);
-
return ret;
}
EXPORT_SYMBOL(vfio_unpin_pages);
@@ -2204,13 +2200,9 @@ int vfio_dma_rw(struct vfio_device *vdev, dma_addr_t user_iova, void *data,
struct vfio_iommu_driver *driver;
int ret = 0;

- if (!data || len <= 0)
+ if (!data || len <= 0 || !vfio_assert_device_open(vdev))
return -EINVAL;

- ret = vfio_group_add_container_user(vdev->group);
- if (ret)
- return ret;
-
container = vdev->group->container;
driver = container->iommu_driver;

@@ -2219,9 +2211,6 @@ int vfio_dma_rw(struct vfio_device *vdev, dma_addr_t user_iova, void *data,
user_iova, data, len, write);
else
ret = -ENOTTY;
-
- vfio_group_try_dissolve_container(vdev->group);
-
return ret;
}
EXPORT_SYMBOL(vfio_dma_rw);
@@ -2234,10 +2223,6 @@ static int vfio_register_iommu_notifier(struct vfio_group *group,
struct vfio_iommu_driver *driver;
int ret;

- ret = vfio_group_add_container_user(group);
- if (ret)
- return -EINVAL;
-
container = group->container;
driver = container->iommu_driver;
if (likely(driver && driver->ops->register_notifier))
@@ -2245,9 +2230,6 @@ static int vfio_register_iommu_notifier(struct vfio_group *group,
events, nb);
else
ret = -ENOTTY;
-
- vfio_group_try_dissolve_container(group);
-
return ret;
}

@@ -2258,10 +2240,6 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group,
struct vfio_iommu_driver *driver;
int ret;

- ret = vfio_group_add_container_user(group);
- if (ret)
- return -EINVAL;
-
container = group->container;
driver = container->iommu_driver;
if (likely(driver && driver->ops->unregister_notifier))
@@ -2269,9 +2247,6 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group,
nb);
else
ret = -ENOTTY;
-
- vfio_group_try_dissolve_container(group);
-
return ret;
}

@@ -2300,10 +2275,6 @@ static int vfio_register_group_notifier(struct vfio_group *group,
if (*events)
return -EINVAL;

- ret = vfio_group_add_container_user(group);
- if (ret)
- return -EINVAL;
-
ret = blocking_notifier_chain_register(&group->notifier, nb);

/*
@@ -2313,25 +2284,6 @@ static int vfio_register_group_notifier(struct vfio_group *group,
if (!ret && set_kvm && group->kvm)
blocking_notifier_call_chain(&group->notifier,
VFIO_GROUP_NOTIFY_SET_KVM, group->kvm);
-
- vfio_group_try_dissolve_container(group);
-
- return ret;
-}
-
-static int vfio_unregister_group_notifier(struct vfio_group *group,
- struct notifier_block *nb)
-{
- int ret;
-
- ret = vfio_group_add_container_user(group);
- if (ret)
- return -EINVAL;
-
- ret = blocking_notifier_chain_unregister(&group->notifier, nb);
-
- vfio_group_try_dissolve_container(group);
-
return ret;
}

@@ -2341,7 +2293,7 @@ int vfio_register_notifier(struct vfio_device *dev, enum vfio_notify_type type,
struct vfio_group *group = dev->group;
int ret;

- if (!nb || !events || (*events == 0))
+ if (!nb || !events || (*events == 0) || !vfio_assert_device_open(dev))
return -EINVAL;

switch (type) {
@@ -2365,7 +2317,7 @@ int vfio_unregister_notifier(struct vfio_device *dev,
struct vfio_group *group = dev->group;
int ret;

- if (!nb)
+ if (!nb || !vfio_assert_device_open(dev))
return -EINVAL;

switch (type) {
@@ -2373,7 +2325,7 @@ int vfio_unregister_notifier(struct vfio_device *dev,
ret = vfio_unregister_iommu_notifier(group, nb);
break;
case VFIO_GROUP_NOTIFY:
- ret = vfio_unregister_group_notifier(group, nb);
+ ret = blocking_notifier_chain_unregister(&group->notifier, nb);
break;
default:
ret = -EINVAL;
--
2.36.0