linux-kernel - Re: [PATCH v2] iio: core: fix ioctl handlers removal

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Message-ID: <YIQKgLtdUlSHsJXu@arch>
Date:   Sat, 24 Apr 2021 14:09:36 +0200
From:   Tomasz Duszynski <tomasz.duszynski@...akon.com>
To:     Jonathan Cameron <jic23@...nel.org>
CC:     Tomasz Duszynski <tomasz.duszynski@...akon.com>,
        <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <lars@...afoo.de>, <ardeleanalex@...il.com>
Subject: Re: [PATCH v2] iio: core: fix ioctl handlers removal

On Sat, Apr 24, 2021 at 11:52:50AM +0100, Jonathan Cameron wrote:
> On Fri, 23 Apr 2021 10:02:44 +0200
> Tomasz Duszynski <tomasz.duszynski@...akon.com> wrote:
>
> > Currently ioctl handlers are removed twice. For the first time during
> > iio_device_unregister() then later on inside
> > iio_device_unregister_eventset() and iio_buffers_free_sysfs_and_mask().
> > Double free leads to kernel panic.
> >
> > Fix this by not touching ioctl handlers list directly but rather
> > letting code responsible for registration call the matching cleanup
> > routine itself.
> >
> > Fixes: 8dedcc3eee3ac ("iio: core: centralize ioctl() calls to the main chardev")
> > Signed-off-by: Tomasz Duszynski <tomasz.duszynski@...akon.com>
> > Acked-by: Alexandru Ardelean <ardeleanalex@...il.com>
>
> There are a bunch of unused local variables as a result of this change
> (build warnings on my standard W=1 C=1 test).  I've dropped those as well and
> applied this to the fixes-togreg branch of iio.git.
>

Right, thanks for catching this.

> We are a bit unfortunate on timing for this as I won't send a pull request
> for fixes until towards the end of the merge window.  I've marked it for stable
> though so it should filter back fairly quickly so kernels people actually
> use.
>
> Thanks,
>
> Jonathan
>
> > ---
> > v2:
> > * add fixes tag and ack
> >
> >  drivers/iio/industrialio-core.c | 3 ---
> >  1 file changed, 3 deletions(-)
> >
> > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> > index d92c58a94fe4..98944cfc7331 100644
> > --- a/drivers/iio/industrialio-core.c
> > +++ b/drivers/iio/industrialio-core.c
> > @@ -1939,9 +1939,6 @@ void iio_device_unregister(struct iio_dev *indio_dev)
> >
> >  	indio_dev->info = NULL;
> >
> > -	list_for_each_entry_safe(h, t, &iio_dev_opaque->ioctl_handlers, entry)
> > -		list_del(&h->entry);
> > -
> >  	iio_device_wakeup_eventset(indio_dev);
> >  	iio_buffer_wakeup_poll(indio_dev);
> >
> > --
> > 2.31.1
> >
>