linux-kernel - Re: [PATCH v2 0/5] iio: treewide: rearrange iio trig get/register

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Date:   Sat, 28 May 2022 18:10:04 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Dmitry Rokosov <DDRokosov@...rdevices.ru>
Cc:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "lorenzo.bianconi83@...il.com" <lorenzo.bianconi83@...il.com>,
        "srinivas.pandruvada@...ux.intel.com" 
        <srinivas.pandruvada@...ux.intel.com>,
        "teodora.baluta@...el.com" <teodora.baluta@...el.com>,
        "narcisaanamaria12@...il.com" <narcisaanamaria12@...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 v2 0/5] iio: treewide: rearrange iio trig get/register

On Tue, 24 May 2022 18:14:37 +0000
Dmitry Rokosov <DDRokosov@...rdevices.ru> wrote:

> The following patchset resolves problems with iio_trigger_get() and
> iio_trigger_register() call order in the different IIO drivers.
> 
> IIO trigger interface function iio_trigger_get() should be called after
> iio_trigger_register() (or its devm analogue) strictly, because of
> iio_trigger_get() acquires module refcnt based on the trigger->owner
> pointer, which is initialized inside iio_trigger_register() to
> THIS_MODULE.
> If this call order is wrong, the next iio_trigger_put() (from sysfs
> callback or "delete module" path) will dereference "default" module
> refcnt, which is incorrect behaviour.

Hi Dmitry,

Series applied to the fixes-togreg branch of iio.git and marked for stable.

Do you think it's also worth adding a runtime warning in iio_trigger_get()
on !trig->owner so that we catch any cases of this introduced in the future?

Thanks,

Jonathan

> 
> Changes v1->v2:
>     - provide tag Fixes: for all patches
> 
> Dmitry Rokosov (5):
>   iio:accel:bma180: rearrange iio trigger get and register
>   iio:accel:kxcjk-1013: rearrange iio trigger get and register
>   iio:accel:mxc4005: rearrange iio trigger get and register
>   iio:chemical:ccs811: rearrange iio trigger get and register
>   iio:humidity:hts221: rearrange iio trigger get and register
> 
>  drivers/iio/accel/bma180.c           | 3 ++-
>  drivers/iio/accel/kxcjk-1013.c       | 4 ++--
>  drivers/iio/accel/mxc4005.c          | 4 ++--
>  drivers/iio/chemical/ccs811.c        | 4 ++--
>  drivers/iio/humidity/hts221_buffer.c | 5 ++++-
>  5 files changed, 12 insertions(+), 8 deletions(-)
>