Re: [PATCH v3 02/10] usb: roles: Handle driver reference counting

[Hans de Goede]

HI,

On 04-09-18 13:22, Heikki Krogerus wrote:

This fixes potential "BUG: unable to handle kernel paging
request at ..." from happening.

Fixes: fde0aa6c175a ("usb: common: Small class for USB role switches")
Cc: <sta...@vger.kernel.org>
Signed-off-by: Heikki Krogerus <heikki.kroge...@linux.intel.com>
---
  drivers/usb/common/roles.c | 15 ++++++++++++---
  1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/common/roles.c b/drivers/usb/common/roles.c
index 15cc76e22123..3d8a776e55ee 100644
--- a/drivers/usb/common/roles.c
+++ b/drivers/usb/common/roles.c
@@ -109,8 +109,15 @@ static void *usb_role_switch_match(struct 
device_connection *con, int ep,
   */
  struct usb_role_switch *usb_role_switch_get(struct device *dev)
  {
-       return device_connection_find_match(dev, "usb-role-switch", NULL,
-                                           usb_role_switch_match);
+       struct usb_role_switch *sw;
+
+       sw = device_connection_find_match(dev, "usb-role-switch", NULL,
+                                         usb_role_switch_match);
+
+       if (!IS_ERR(sw))
+               WARN_ON(!try_module_get(sw->dev.parent->driver->owner));

While testing I found a bug, so sorry but this is going to need a v4,
device_connection_find_match() may return NULL here, so this needs
to be if (!IS_ERR_OR_NULL(sw)) to avoid an oops.

Note I'm also seeing some other issues which I need to debug I will
do so tomorrow morning so you may want to wait a bit with v4.

Regards,

Hans

+
+       return sw;
  }
  EXPORT_SYMBOL_GPL(usb_role_switch_get);

@@ -122,8 +129,10 @@ EXPORT_SYMBOL_GPL(usb_role_switch_get);

   */
  void usb_role_switch_put(struct usb_role_switch *sw)
  {
-       if (!IS_ERR_OR_NULL(sw))
+       if (!IS_ERR_OR_NULL(sw)) {
                put_device(&sw->dev);
+               module_put(sw->dev.parent->driver->owner);
+       }
  }
  EXPORT_SYMBOL_GPL(usb_role_switch_put);