linux-kernel - Re: [PATCH v1] iio: trigger: warn about non-registered iio trigger getting attempt

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Message-ID: <20220601103356.xlimabcihaay5jky@CAB-WSD-L081021.sigma.sbrf.ru>
Date:   Wed, 1 Jun 2022 10:33:46 +0000
From:   Dmitry Rokosov <DDRokosov@...rdevices.ru>
To:     Nuno Sá <noname.nuno@...il.com>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] iio: trigger: warn about non-registered iio trigger
 getting attempt

Hi Nuno,

Thank you for comments!

On Wed, Jun 01, 2022 at 10:47:54AM +0200, Nuno Sá wrote:
> On Tue, 2022-05-31 at 18:57 +0000, Dmitry Rokosov wrote:
> > Hi Jonathan,
> > 
> > I have one question about a cases when trigger owner is builtin
> > module.
> > In the such cases trig->owner == null, because THIS_MODULE equals to
> > null. How do you think, should we take into account such situations?
> > 
> > IMHO we have to take in and save this information to trig_info during
> > trigger allocation call. For example we can check THIS_MODULE from
> > the
> 
> Hmmm, If we were to do something during iio_trigger_alloc(), we would
> rather assign already THIS_MODULE to owner and we would not need this
> WARN(). I mean, if someone calls iio_trigger_get() before allocating
> it, it will have bigger problems :).
> 

You are right, non-allocated pointer dereference is much bigger problem :)

> I think this could actually be something reasonable...

I think it could be a good solution, but it's required a lot of changes
in the IIO drivers code, because if we assign trig->owner from
iio_trigger_alloc(), we do not need this_mod parameter in the
iio_trigger_register() iface and its wrappers.
So it means to make it workable we must:
    - rework iio_trigger_alloc()
    - redesign iio_trigger_register() iface and its wrappers
    - correct iio_trigger_register() call from all IIO drivers

I suppose we need to wait for Jonathan's comments here...

-- 
Thank you,
Dmitry