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Subject[RFC] Input: Remove unsafe device module references
Date
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 <dh.herrmann@googlemail.com>
---
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


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