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

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Message-ID: <1510690474.18523.39.camel@codethink.co.uk>
Date:   Tue, 14 Nov 2017 20:14:34 +0000
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alison Schofield <amsfield22@...il.com>,
        Jonathan Cameron <jic23@...nel.org>
Cc:     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 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?

Ben.

> Signed-off-by: Alison Schofield <amsfield22@...il.com>
> Signed-off-by: Jonathan Cameron <jic23@...nel.org>
> Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  drivers/iio/trigger/iio-trig-interrupt.c          |    8 ++++----
>  drivers/iio/trigger/iio-trig-sysfs.c              |    2 +-
>  drivers/staging/iio/trigger/iio-trig-bfin-timer.c |    4 ++--
>  3 files changed, 7 insertions(+), 7 deletions(-)
> 
> --- a/drivers/iio/trigger/iio-trig-interrupt.c
> +++ b/drivers/iio/trigger/iio-trig-interrupt.c
> @@ -58,7 +58,7 @@ static int iio_interrupt_trigger_probe(s
>  	trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
>  	if (!trig_info) {
>  		ret = -ENOMEM;
> -		goto error_put_trigger;
> +		goto error_free_trigger;
>  	}
>  	iio_trigger_set_drvdata(trig, trig_info);
>  	trig_info->irq = irq;
> @@ -83,8 +83,8 @@ error_release_irq:
>  	free_irq(irq, trig);
>  error_free_trig_info:
>  	kfree(trig_info);
> -error_put_trigger:
> -	iio_trigger_put(trig);
> +error_free_trigger:
> +	iio_trigger_free(trig);
>  error_ret:
>  	return ret;
>  }
> @@ -99,7 +99,7 @@ static int iio_interrupt_trigger_remove(
>  	iio_trigger_unregister(trig);
>  	free_irq(trig_info->irq, trig);
>  	kfree(trig_info);
> -	iio_trigger_put(trig);
> +	iio_trigger_free(trig);
>  
>  	return 0;
>  }
> --- a/drivers/iio/trigger/iio-trig-sysfs.c
> +++ b/drivers/iio/trigger/iio-trig-sysfs.c
> @@ -174,7 +174,7 @@ static int iio_sysfs_trigger_probe(int i
>  	return 0;
>  
>  out2:
> -	iio_trigger_put(t->trig);
> +	iio_trigger_free(t->trig);
>  free_t:
>  	kfree(t);
>  out1:
> --- a/drivers/staging/iio/trigger/iio-trig-bfin-timer.c
> +++ b/drivers/staging/iio/trigger/iio-trig-bfin-timer.c
> @@ -259,7 +259,7 @@ out_free_irq:
>  out1:
>  	iio_trigger_unregister(st->trig);
>  out:
> -	iio_trigger_put(st->trig);
> +	iio_trigger_free(st->trig);
>  	return ret;
>  }
>  
> @@ -272,7 +272,7 @@ static int iio_bfin_tmr_trigger_remove(s
>  		peripheral_free(st->t->pin);
>  	free_irq(st->irq, st);
>  	iio_trigger_unregister(st->trig);
> -	iio_trigger_put(st->trig);
> +	iio_trigger_free(st->trig);
>  
>  	return 0;
>  }
> 
> 
> 
-- 
Ben Hutchings
Software Developer, Codethink Ltd.