Drivers: hv: vmbus: use generic driver_override infrastructure

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]

Tested-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/
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")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/20260505133935.3772495-4-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index d28ff45d4cfddd3262bdd034fe52dd01ea0866b1..acfb579828c537b4ad1b6d4eb9532c17bf6104b8 100644 (file)
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -538,34 +538,6 @@ 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,
@@ -596,7 +568,6 @@ 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,
 };
 
@@ -708,9 +679,11 @@ 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))
+       /* If a driver override is set, only bind to the matching driver */
+       ret = device_match_driver_override(&dev->device, &drv->driver);
+       if (ret == 0)
                return NULL;
 
        /* Look at the dynamic ids first, before the static ones */
@@ -718,8 +691,11 @@ static const struct hv_vmbus_device_id *hv_vmbus_get_id(const struct hv_driver *
        if (!id)
                id = hv_vmbus_dev_match(drv->id_table, guid);
 
-       /* driver_override will always match, send a dummy id */
-       if (!id && dev->driver_override)
+       /*
+        * If there's a matching driver override, this function should succeed,
+        * thus return a dummy device ID if no matching ID is found.
+        */
+       if (!id && ret > 0)
                id = &vmbus_device_null;
 
        return id;
@@ -1021,6 +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 964f1be8150c591c551b99ee437102b656557b4d..c054d7eff622dc3b34dea6ab7aac7ff7ffaee7eb 100644 (file)
--- 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;