[PATCH 08/12] vdpa: use generic driver_override infrastructure

Danilo Krummrich
2026-03-24T01:00:49Z

When a driver is probed through __driver_attach(), the bus' match()
callback is called without the device lock held, thus accessing the
driver_override field without a lock, which can cause a UAF.

Fix this by using the driver-core driver_override infrastructure taking
care of proper locking internally.

Note that calling match() from __driver_attach() without the device lock
held is intentional. [1]

Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [1]
Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
Fixes: 539fec78edb4 ("vdpa: add driver_override support")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
drivers/vdpa/vdpa.c | 48 +++++---------------------------------------
include/linux/vdpa.h | 4 ----
2 files changed, 5 insertions(+), 47 deletions(-)

diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
index 34874beb0152..caf0ee5d6856 100644
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -67,57 +67,20 @@ static void vdpa_dev_remove(struct device *d)

static int vdpa_dev_match(struct device *dev, const struct device_driver *drv)
{
- struct vdpa_device *vdev = dev_to_vdpa(dev);
+ int ret;

/* Check override first, and if set, only use the named driver */
- if (vdev->driver_override)
- return strcmp(vdev->driver_override, drv->name) == 0;
+ ret = device_match_driver_override(dev, drv);
+ if (ret >= 0)
+ return ret;

/* Currently devices must be supported by all vDPA bus drivers */
return 1;
}

-static ssize_t driver_override_store(struct device *dev,
- struct device_attribute *attr,
- const char *buf, size_t count)
-{
- struct vdpa_device *vdev = dev_to_vdpa(dev);
- int ret;
-
- ret = driver_set_override(dev, &vdev->driver_override, buf, count);
- if (ret)
- return ret;
-
- return count;
-}
-
-static ssize_t driver_override_show(struct device *dev,
- struct device_attribute *attr, char *buf)
-{
- struct vdpa_device *vdev = dev_to_vdpa(dev);
- ssize_t len;
-
- device_lock(dev);
- len = sysfs_emit(buf, "%s\n", vdev->driver_override);
- device_unlock(dev);
-
- return len;
-}
-static DEVICE_ATTR_RW(driver_override);
-
-static struct attribute *vdpa_dev_attrs[] = {
- &dev_attr_driver_override.attr,
- NULL,
-};
-
-static const struct attribute_group vdpa_dev_group = {
- .attrs = vdpa_dev_attrs,
-};
-__ATTRIBUTE_GROUPS(vdpa_dev);
-
static const struct bus_type vdpa_bus = {
.name = "vdpa",
- .dev_groups = vdpa_dev_groups,
+ .driver_override = true,
.match = vdpa_dev_match,
.probe = vdpa_dev_probe,
.remove = vdpa_dev_remove,
@@ -132,7 +95,6 @@ static void vdpa_release_dev(struct device *d)
ops->free(vdev);

ida_free(&vdpa_index_ida, vdev->index);
- kfree(vdev->driver_override);
kfree(vdev);
}

diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index 2bfe3baa63f4..782c42d25db1 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -72,9 +72,6 @@ struct vdpa_mgmt_dev;
* struct vdpa_device - representation of a vDPA device
* @dev: underlying device
* @vmap: the metadata passed to upper layer to be used for mapping
- * @driver_override: driver name to force a match; do not set directly,
- * because core frees it; use driver_set_override() to
- * set or clear it.
* @config: the configuration ops for this device.
* @map: the map ops for this device
* @cf_lock: Protects get and set access to configuration layout.
@@ -90,7 +87,6 @@ struct vdpa_mgmt_dev;
struct vdpa_device {
struct device dev;
union virtio_map vmap;
- const char *driver_override;
const struct vdpa_config_ops *config;
const struct virtio_map_ops *map;
struct rw_semaphore cf_lock; /* Protects get/set config */
--
2.53.0