[PATCH 04/12] hv: vmbus: use generic driver_override infrastructure

Danilo Krummrich
2026-03-24T01:00:11Z

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: d765edbb301c ("vmbus: add driver_override support")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
drivers/hv/vmbus_drv.c | 36 +++++-------------------------------
include/linux/hyperv.h | 5 -----
2 files changed, 5 insertions(+), 36 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index bc4fc1951ae1..bc8dfd136f3c 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -541,34 +541,6 @@ static ssize_t device_show(struct device *dev,
}
static DEVICE_ATTR_RO(device);

-static ssize_t driver_override_store(struct device *dev,
- struct device_attribute *attr,
- const char *buf, size_t count)
-{
- struct hv_device *hv_dev = device_to_hv_device(dev);
- int ret;
-
- ret = driver_set_override(dev, &hv_dev->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 hv_device *hv_dev = device_to_hv_device(dev);
- ssize_t len;
-
- device_lock(dev);
- len = sysfs_emit(buf, "%s\n", hv_dev->driver_override);
- device_unlock(dev);
-
- return len;
-}
-static DEVICE_ATTR_RW(driver_override);
-
/* Set up per device attributes in /sys/bus/vmbus/devices/<bus device> */
static struct attribute *vmbus_dev_attrs[] = {
&dev_attr_id.attr,
@@ -599,7 +571,6 @@ static struct attribute *vmbus_dev_attrs[] = {
&dev_attr_channel_vp_mapping.attr,
&dev_attr_vendor.attr,
&dev_attr_device.attr,
- &dev_attr_driver_override.attr,
NULL,
};

@@ -711,9 +682,11 @@ static const struct hv_vmbus_device_id *hv_vmbus_get_id(const struct hv_driver *
{
const guid_t *guid = &dev->dev_type;
const struct hv_vmbus_device_id *id;
+ int ret;

/* When driver_override is set, only bind to the matching driver */
- if (dev->driver_override && strcmp(dev->driver_override, drv->name))
+ ret = device_match_driver_override(&dev->device, &drv->driver);
+ if (ret == 0)
return NULL;

/* Look at the dynamic ids first, before the static ones */
@@ -722,7 +695,7 @@ static const struct hv_vmbus_device_id *hv_vmbus_get_id(const struct hv_driver *
id = hv_vmbus_dev_match(drv->id_table, guid);

/* driver_override will always match, send a dummy id */
- if (!id && dev->driver_override)
+ if (!id && ret > 0)
id = &vmbus_device_null;

return id;
@@ -1024,6 +997,7 @@ static const struct dev_pm_ops vmbus_pm = {
/* The one and only one */
static const struct bus_type hv_bus = {
.name = "vmbus",
+ .driver_override = true,
.match = vmbus_match,
.shutdown = vmbus_shutdown,
.remove = vmbus_remove,
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index dfc516c1c719..bf689d07d750 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1272,11 +1272,6 @@ struct hv_device {
u16 device_id;

struct device device;
- /*
- * Driver name to force a match. Do not set directly, because core
- * frees it. Use driver_set_override() to set or clear it.
- */
- const char *driver_override;

struct vmbus_channel *channel;
struct kset *channels_kset;
--
2.53.0