[PATCH 5.11 006/601] usb: roles: Call try_module_get() from usb_role_switch_find_by_fwnode()

[Greg Kroah-Hartman]

From: Hans de Goede <hdegoede@xxxxxxxxxx>

commit 3a2a91a2d51761557843996a66098eb7182b48b4 upstream.

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()")
Cc: stable <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210409124136.65591-1-hdegoede@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/roles/class.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/usb/roles/class.c
+++ b/drivers/usb/roles/class.c
@@ -189,6 +189,8 @@ usb_role_switch_find_by_fwnode(const str
 		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;
 }