On Mon, Jan 29, 2024 at 05:37:38PM +0800, Xu Yang wrote:
> In current design, usb role class driver will get usb_role_switch parent's
> module reference after the user get usb_role_switch device and put the
> reference after the user put the usb_role_switch device. However, the
> parent device of usb_role_switch may be removed before the user put the
> usb_role_switch. If so, then, NULL pointer issue will be met when the user
> put the parent module's reference.
>
> This will save the module pointer in structure of usb_role_switch. Then,
> we don't need to find module by iterating long relations.
>
> Fixes: 5c54fcac9a9d ("usb: roles: Take care of driver module reference counting")
> cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Xu Yang <xu.yang_2@xxxxxxx>
Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> Changes in v2:
> - save module pointer as a member of usb_role_switch as suggested by Alan
> Changes in v3:
> - no changes
> ---
> drivers/usb/roles/class.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index ae41578bd014..2bad038fb9ad 100644
> --- a/drivers/usb/roles/class.c
> +++ b/drivers/usb/roles/class.c
> @@ -21,6 +21,7 @@ static const struct class role_class = {
> struct usb_role_switch {
> struct device dev;
> struct mutex lock; /* device lock*/
> + struct module *module; /* the module this device depends on */
> enum usb_role role;
>
> /* From descriptor */
> @@ -135,7 +136,7 @@ struct usb_role_switch *usb_role_switch_get(struct device *dev)
> usb_role_switch_match);
>
> if (!IS_ERR_OR_NULL(sw))
> - WARN_ON(!try_module_get(sw->dev.parent->driver->owner));
> + WARN_ON(!try_module_get(sw->module));
>
> return sw;
> }
> @@ -157,7 +158,7 @@ struct usb_role_switch *fwnode_usb_role_switch_get(struct fwnode_handle *fwnode)
> sw = fwnode_connection_find_match(fwnode, "usb-role-switch",
> NULL, usb_role_switch_match);
> if (!IS_ERR_OR_NULL(sw))
> - WARN_ON(!try_module_get(sw->dev.parent->driver->owner));
> + WARN_ON(!try_module_get(sw->module));
>
> return sw;
> }
> @@ -172,7 +173,7 @@ EXPORT_SYMBOL_GPL(fwnode_usb_role_switch_get);
> void usb_role_switch_put(struct usb_role_switch *sw)
> {
> if (!IS_ERR_OR_NULL(sw)) {
> - module_put(sw->dev.parent->driver->owner);
> + module_put(sw->module);
> put_device(&sw->dev);
> }
> }
> @@ -189,15 +190,18 @@ struct usb_role_switch *
> usb_role_switch_find_by_fwnode(const struct fwnode_handle *fwnode)
> {
> struct device *dev;
> + struct usb_role_switch *sw = NULL;
>
> if (!fwnode)
> return NULL;
>
> dev = class_find_device_by_fwnode(&role_class, fwnode);
> - if (dev)
> - WARN_ON(!try_module_get(dev->parent->driver->owner));
> + if (dev) {
> + sw = to_role_switch(dev);
> + WARN_ON(!try_module_get(sw->module));
> + }
>
> - return dev ? to_role_switch(dev) : NULL;
> + return sw;
> }
> EXPORT_SYMBOL_GPL(usb_role_switch_find_by_fwnode);
>
> @@ -338,6 +342,7 @@ usb_role_switch_register(struct device *parent,
> sw->set = desc->set;
> sw->get = desc->get;
>
> + sw->module = parent->driver->owner;
> sw->dev.parent = parent;
> sw->dev.fwnode = desc->fwnode;
> sw->dev.class = &role_class;
> --
> 2.34.1
--
heikki
