[PATCH v2] usb: roles: Call try_module_get() from usb_role_switch_find_by_fwnode()

From: Hans de Goede <hdegoede@redhat.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>, linux-usb@vger.kernel.org
Subject: [PATCH v2] usb: roles: Call try_module_get() from usb_role_switch_find_by_fwnode()
Date: Fri,  9 Apr 2021 14:41:36 +0200	[thread overview]
Message-ID: <20210409124136.65591-1-hdegoede@redhat.com> (raw)

usb_role_switch_find_by_fwnode() returns a reference to the role-switch
which must be put by calling usb_role_switch_put().

usb_role_switch_put() calls module_put(sw->dev.parent->driver->owner),
add a matching try_module_get() to usb_role_switch_find_by_fwnode(),
making it behave the same as the other usb_role_switch functions
which return a reference.

This avoids a WARN_ON being hit at kernel/module.c:1158 due to the
module-refcount going below 0.

Fixes: c6919d5e0cd1 ("usb: roles: Add usb_role_switch_find_by_fwnode()")
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
- Fix typo in Subject
- Add Fixes tag
---
 drivers/usb/roles/class.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
index 97f37077b7f9..33b637d0d8d9 100644
--- a/drivers/usb/roles/class.c
+++ b/drivers/usb/roles/class.c
@@ -189,6 +189,8 @@ usb_role_switch_find_by_fwnode(const struct fwnode_handle *fwnode)
 		return NULL;
 
 	dev = class_find_device_by_fwnode(role_class, fwnode);
+	if (dev)
+		WARN_ON(!try_module_get(dev->parent->driver->owner));
 
 	return dev ? to_role_switch(dev) : NULL;
 }
-- 
2.30.2

