linux-kernel - Re: [PATCH 4.4 13/56] iio: trigger: free trigger resource correctly

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Date:   Wed, 15 Nov 2017 17:11:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ben Hutchings <ben.hutchings@...ethink.co.uk>
Cc:     Alison Schofield <amsfield22@...il.com>,
        Jonathan Cameron <jic23@...nel.org>, stable@...r.kernel.org,
        Sasha Levin <alexander.levin@...izon.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4.4 13/56] iio: trigger: free trigger resource correctly

On Tue, Nov 14, 2017 at 08:14:34PM +0000, Ben Hutchings wrote:
> On Mon, 2017-11-13 at 13:55 +0100, Greg Kroah-Hartman wrote:
> > 4.4-stable review patch.  If anyone has any objections, please let me
> > know.
> > 
> > ------------------
> > 
> > From: Alison Schofield <amsfield22@...il.com>
> > 
> > 
> > [ Upstream commit 10e840dfb0b7fc345082dd9e5fff3c1c02e7690e ]
> > 
> > These stand-alone trigger drivers were using iio_trigger_put()
> > where they should have been using iio_trigger_free().  The
> > iio_trigger_put() adds a module_put which is bad since they
> > never did a module_get.
> > 
> > In the sysfs driver, module_get/put's are used as triggers are
> > added & removed. This extra module_put() occurs on an error path
> > in the probe routine (probably rare).
> > 
> > In the bfin-timer & interrupt trigger drivers, the module resources
> > are not explicitly managed, so it's doing a put on something that
> > was never get'd.  It occurs on the probe error path and on the
> > remove path (not so rare).
> > 
> > Tested with the sysfs trigger driver.
> > The bfin & interrupt drivers were build tested & inspected only.
> 
> In 4.4 the iio-trig-periodic-rtc seems to have the same bug (it has
> been removed upstream).  Would it make sense to fix it in 4.4?

Probably, or if it has been removed for a good reason, we can always
remove it in 4.4 :)

thanks,

greg k-h