From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Herrmann Subject: [RFC] Input: Remove unsafe device module references Date: Tue, 1 Nov 2011 16:41:40 +0100 Message-ID: <1320162100-13494-1-git-send-email-dh.herrmann@googlemail.com> Return-path: Received: from mail-fx0-f46.google.com ([209.85.161.46]:54432 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752092Ab1KAPmR (ORCPT ); Tue, 1 Nov 2011 11:42:17 -0400 Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: linux-input@vger.kernel.org Cc: dmitry.torokhov@gmail.com, gregkh@suse.de, linux-kernel@vger.kernel.org, David Herrmann Hi Dmitry and Greg It doesn't make sense to take a reference to our own module. When we call module_put(THIS_MODULE) we cannot make sure that our module is still alive when this function returns. Therefore, module_put() will return to invalid memory and our input_dev_release() function is no longer available. It would be interesting if Greg could elaborate what else we could do to replace this module-refcount as it is definitely needed here. However, "struct device" doesn't provide an owner field so there is no way for us to let the device core keep a reference to our module. I have no clue what to do here but the current implementation is definitely unsafe so this is marked as RFC. Currently, the device_attributes probably already keep a reference to our module so applying this patch would probably not break anything, however, this does not look like something we can trust on. My bug-thread kind of died (https://lkml.org/lkml/2011/10/29/75) so I now try to show this with an example here. Regards David Signed-off-by: David Herrmann --- drivers/input/input.c | 4 ---- 1 files changed, 0 insertions(+), 4 deletions(-) diff --git a/drivers/input/input.c b/drivers/input/input.c index da38d97..f691502 100644 --- a/drivers/input/input.c +++ b/drivers/input/input.c @@ -1417,8 +1417,6 @@ static void input_dev_release(struct device *device) input_mt_destroy_slots(dev); kfree(dev->absinfo); kfree(dev); - - module_put(THIS_MODULE); } /* @@ -1657,8 +1655,6 @@ struct input_dev *input_allocate_device(void) spin_lock_init(&dev->event_lock); INIT_LIST_HEAD(&dev->h_list); INIT_LIST_HEAD(&dev->node); - - __module_get(THIS_MODULE); } return dev; -- 1.7.7.1