[PATCH 5.17 122/219] vfio/pci: Fix vf_token mechanism when device-specific VF drivers are used

Greg Kroah-Hartman
2022-04-18T12:27:45Z

From: Jason Gunthorpe <jgg@nvidia.com>

[ Upstream commit 1ef3342a934e235aca72b4bcc0d6854d80a65077 ]

get_pf_vdev() tries to check if a PF is a VFIO PF by looking at the driver:

if (pci_dev_driver(physfn) != pci_dev_driver(vdev->pdev)) {

However now that we have multiple VF and PF drivers this is no longer
reliable.

This means that security tests realted to vf_token can be skipped by
mixing and matching different VFIO PCI drivers.

Instead of trying to use the driver core to find the PF devices maintain a
linked list of all PF vfio_pci_core_device's that we have called
pci_enable_sriov() on.

When registering a VF just search the list to see if the PF is present and
record the match permanently in the struct. PCI core locking prevents a PF
from passing pci_disable_sriov() while VF drivers are attached so the VFIO
owned PF becomes a static property of the VF.

In common cases where vfio does not own the PF the global list remains
empty and the VF's pointer is statically NULL.

This also fixes a lockdep splat from recursive locking of the
vfio_group::device_lock between vfio_device_get_from_name() and
vfio_device_get_from_dev(). If the VF and PF share the same group this
would deadlock.

Fixes: ff53edf6d6ab ("vfio/pci: Split the pci_driver code out of vfio_pci_core.c")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/0-v3-876570980634+f2e8-vfio_vf_token_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/vfio/pci/vfio_pci_core.c | 124 ++++++++++++++++++-------------
include/linux/vfio_pci_core.h | 2 +
2 files changed, 76 insertions(+), 50 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 2e6409cc11ad..ef54ef11af55 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -36,6 +36,10 @@ static bool nointxmask;
static bool disable_vga;
static bool disable_idle_d3;

+/* List of PF's that vfio_pci_core_sriov_configure() has been called on */
+static DEFINE_MUTEX(vfio_pci_sriov_pfs_mutex);
+static LIST_HEAD(vfio_pci_sriov_pfs);
+
static inline bool vfio_vga_disabled(void)
{
#ifdef CONFIG_VFIO_PCI_VGA
@@ -434,47 +438,17 @@ void vfio_pci_core_disable(struct vfio_pci_core_device *vdev)
}
EXPORT_SYMBOL_GPL(vfio_pci_core_disable);

-static struct vfio_pci_core_device *get_pf_vdev(struct vfio_pci_core_device *vdev)
-{
- struct pci_dev *physfn = pci_physfn(vdev->pdev);
- struct vfio_device *pf_dev;
-
- if (!vdev->pdev->is_virtfn)
- return NULL;
-
- pf_dev = vfio_device_get_from_dev(&physfn->dev);
- if (!pf_dev)
- return NULL;
-
- if (pci_dev_driver(physfn) != pci_dev_driver(vdev->pdev)) {
- vfio_device_put(pf_dev);
- return NULL;
- }
-
- return container_of(pf_dev, struct vfio_pci_core_device, vdev);
-}
-
-static void vfio_pci_vf_token_user_add(struct vfio_pci_core_device *vdev, int val)
-{
- struct vfio_pci_core_device *pf_vdev = get_pf_vdev(vdev);
-
- if (!pf_vdev)
- return;
-
- mutex_lock(&pf_vdev->vf_token->lock);
- pf_vdev->vf_token->users += val;
- WARN_ON(pf_vdev->vf_token->users < 0);
- mutex_unlock(&pf_vdev->vf_token->lock);
-
- vfio_device_put(&pf_vdev->vdev);
-}
-
void vfio_pci_core_close_device(struct vfio_device *core_vdev)
{
struct vfio_pci_core_device *vdev =
container_of(core_vdev, struct vfio_pci_core_device, vdev);

- vfio_pci_vf_token_user_add(vdev, -1);
+ if (vdev->sriov_pf_core_dev) {
+ mutex_lock(&vdev->sriov_pf_core_dev->vf_token->lock);
+ WARN_ON(!vdev->sriov_pf_core_dev->vf_token->users);
+ vdev->sriov_pf_core_dev->vf_token->users--;
+ mutex_unlock(&vdev->sriov_pf_core_dev->vf_token->lock);
+ }
vfio_spapr_pci_eeh_release(vdev->pdev);
vfio_pci_core_disable(vdev);

@@ -495,7 +469,12 @@ void vfio_pci_core_finish_enable(struct vfio_pci_core_device *vdev)
{
vfio_pci_probe_mmaps(vdev);
vfio_spapr_pci_eeh_open(vdev->pdev);
- vfio_pci_vf_token_user_add(vdev, 1);
+
+ if (vdev->sriov_pf_core_dev) {
+ mutex_lock(&vdev->sriov_pf_core_dev->vf_token->lock);
+ vdev->sriov_pf_core_dev->vf_token->users++;
+ mutex_unlock(&vdev->sriov_pf_core_dev->vf_token->lock);
+ }
}
EXPORT_SYMBOL_GPL(vfio_pci_core_finish_enable);

@@ -1603,11 +1582,8 @@ static int vfio_pci_validate_vf_token(struct vfio_pci_core_device *vdev,
*
* If the VF token is provided but unused, an error is generated.
*/
- if (!vdev->pdev->is_virtfn && !vdev->vf_token && !vf_token)
- return 0; /* No VF token provided or required */
-
if (vdev->pdev->is_virtfn) {
- struct vfio_pci_core_device *pf_vdev = get_pf_vdev(vdev);
+ struct vfio_pci_core_device *pf_vdev = vdev->sriov_pf_core_dev;
bool match;

if (!pf_vdev) {
@@ -1620,7 +1596,6 @@ static int vfio_pci_validate_vf_token(struct vfio_pci_core_device *vdev,
}

if (!vf_token) {
- vfio_device_put(&pf_vdev->vdev);
pci_info_ratelimited(vdev->pdev,
"VF token required to access device\n");
return -EACCES;
@@ -1630,8 +1605,6 @@ static int vfio_pci_validate_vf_token(struct vfio_pci_core_device *vdev,
match = uuid_equal(uuid, &pf_vdev->vf_token->uuid);
mutex_unlock(&pf_vdev->vf_token->lock);

- vfio_device_put(&pf_vdev->vdev);
-
if (!match) {
pci_info_ratelimited(vdev->pdev,
"Incorrect VF token provided for device\n");
@@ -1752,8 +1725,30 @@ static int vfio_pci_bus_notifier(struct notifier_block *nb,
static int vfio_pci_vf_init(struct vfio_pci_core_device *vdev)
{
struct pci_dev *pdev = vdev->pdev;
+ struct vfio_pci_core_device *cur;
+ struct pci_dev *physfn;
int ret;

+ if (pdev->is_virtfn) {
+ /*
+ * If this VF was created by our vfio_pci_core_sriov_configure()
+ * then we can find the PF vfio_pci_core_device now, and due to
+ * the locking in pci_disable_sriov() it cannot change until
+ * this VF device driver is removed.
+ */
+ physfn = pci_physfn(vdev->pdev);
+ mutex_lock(&vfio_pci_sriov_pfs_mutex);
+ list_for_each_entry(cur, &vfio_pci_sriov_pfs, sriov_pfs_item) {
+ if (cur->pdev == physfn) {
+ vdev->sriov_pf_core_dev = cur;
+ break;
+ }
+ }
+ mutex_unlock(&vfio_pci_sriov_pfs_mutex);
+ return 0;
+ }
+
+ /* Not a SRIOV PF */
if (!pdev->is_physfn)
return 0;

@@ -1825,6 +1820,7 @@ void vfio_pci_core_init_device(struct vfio_pci_core_device *vdev,
INIT_LIST_HEAD(&vdev->ioeventfds_list);
mutex_init(&vdev->vma_lock);
INIT_LIST_HEAD(&vdev->vma_list);
+ INIT_LIST_HEAD(&vdev->sriov_pfs_item);
init_rwsem(&vdev->memory_lock);
}
EXPORT_SYMBOL_GPL(vfio_pci_core_init_device);
@@ -1916,7 +1912,7 @@ void vfio_pci_core_unregister_device(struct vfio_pci_core_device *vdev)
{
struct pci_dev *pdev = vdev->pdev;

- pci_disable_sriov(pdev);
+ vfio_pci_core_sriov_configure(pdev, 0);

vfio_unregister_group_dev(&vdev->vdev);

@@ -1954,21 +1950,49 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,

int vfio_pci_core_sriov_configure(struct pci_dev *pdev, int nr_virtfn)
{
+ struct vfio_pci_core_device *vdev;
struct vfio_device *device;
int ret = 0;

+ device_lock_assert(&pdev->dev);
+
device = vfio_device_get_from_dev(&pdev->dev);
if (!device)
return -ENODEV;

- if (nr_virtfn == 0)
- pci_disable_sriov(pdev);
- else
+ vdev = container_of(device, struct vfio_pci_core_device, vdev);
+
+ if (nr_virtfn) {
+ mutex_lock(&vfio_pci_sriov_pfs_mutex);
+ /*
+ * The thread that adds the vdev to the list is the only thread
+ * that gets to call pci_enable_sriov() and we will only allow
+ * it to be called once without going through
+ * pci_disable_sriov()
+ */
+ if (!list_empty(&vdev->sriov_pfs_item)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ list_add_tail(&vdev->sriov_pfs_item, &vfio_pci_sriov_pfs);
+ mutex_unlock(&vfio_pci_sriov_pfs_mutex);
ret = pci_enable_sriov(pdev, nr_virtfn);
+ if (ret)
+ goto out_del;
+ ret = nr_virtfn;
+ goto out_put;
+ }

- vfio_device_put(device);
+ pci_disable_sriov(pdev);

- return ret < 0 ? ret : nr_virtfn;
+out_del:
+ mutex_lock(&vfio_pci_sriov_pfs_mutex);
+ list_del_init(&vdev->sriov_pfs_item);
+out_unlock:
+ mutex_unlock(&vfio_pci_sriov_pfs_mutex);
+out_put:
+ vfio_device_put(device);
+ return ret;
}
EXPORT_SYMBOL_GPL(vfio_pci_core_sriov_configure);

diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index ae6f4838ab75..6e5db4edc335 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -133,6 +133,8 @@ struct vfio_pci_core_device {
struct mutex ioeventfds_lock;
struct list_head ioeventfds_list;
struct vfio_pci_vf_token *vf_token;
+ struct list_head sriov_pfs_item;
+ struct vfio_pci_core_device *sriov_pf_core_dev;
struct notifier_block nb;
struct mutex vma_lock;
struct list_head vma_list;
--
2.35.1