linux-kernel - [PATCH] staging:iio:tsl2563 rewrite probe error handling

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Message-Id: <1330967759-18660-1-git-send-email-grundler@chromium.org>
Date:	Mon,  5 Mar 2012 09:15:59 -0800
From:	Grant Grundler <grundler@...omium.org>
To:	Jonathan Cameron <jic23@....ac.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Benson Leung <bleung@...omium.org>,
	Bryan Freed <bfreed@...omium.org>, linux-iio@...r.kernel.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	Grant Grundler <grundler@...omium.org>
Subject: [PATCH] staging:iio:tsl2563 rewrite probe error handling

tsl2563 probe function has two minor issues with it's error handling paths:
1) it is silent (did not report errors to dmesg)
2) did not return failure code (mixed up use of ret and err)

and two major issues:
3) goto fail2 would corrupt a free memory pool ("double free")
4) device registration failure did NOT cancel/flush delayed work.
   (and thus dereference a freed data structure later)

The "double free" is subtle and was introduced with this change:
    Author: Jonathan Cameron <jic23@....ac.uk>
    Date:   Mon Apr 18 12:58:55 2011 +0100
    staging:iio:tsl2563 take advantage of new iio_device_allocate private data.

Originally, chip was allocated seperately. Now it's appended to the
indio_dev by iio_allocate_device(sizeof(*chip)). So we only need one
kfree call as well (in iio_free_device()).

Signed-off-by: Grant Grundler <grundler@...omium.org>
---
 Gory details of tracking this down are here:
    http://crosbug.com/26819

 Despite iio_device_registration failing, system can at least now boot.
 Will follow up with a fix to "double register : in_intensity_both_raw"
 error that is included in the bug report.

 drivers/staging/iio/light/tsl2563.c |   39 +++++++++++++++++++++++-----------
 1 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/drivers/staging/iio/light/tsl2563.c b/drivers/staging/iio/light/tsl2563.c
index 7e984bc..bf6498b 100644
--- a/drivers/staging/iio/light/tsl2563.c
+++ b/drivers/staging/iio/light/tsl2563.c
@@ -705,7 +705,6 @@ static int __devinit tsl2563_probe(struct i2c_client *client,
 	struct tsl2563_chip *chip;
 	struct tsl2563_platform_data *pdata = client->dev.platform_data;
 	int err = 0;
-	int ret;
 	u8 id = 0;
 
 	indio_dev = iio_allocate_device(sizeof(*chip));
@@ -719,13 +718,15 @@ static int __devinit tsl2563_probe(struct i2c_client *client,
 
 	err = tsl2563_detect(chip);
 	if (err) {
-		dev_err(&client->dev, "device not found, error %d\n", -err);
+		dev_err(&client->dev, "detect error %d\n", -err);
 		goto fail1;
 	}
 
 	err = tsl2563_read_id(chip, &id);
-	if (err)
+	if (err) {
+		dev_err(&client->dev, "read id error %d\n", -err);
 		goto fail1;
+	}
 
 	mutex_init(&chip->lock);
 
@@ -748,40 +749,52 @@ static int __devinit tsl2563_probe(struct i2c_client *client,
 	indio_dev->num_channels = ARRAY_SIZE(tsl2563_channels);
 	indio_dev->dev.parent = &client->dev;
 	indio_dev->modes = INDIO_DIRECT_MODE;
+
 	if (client->irq)
 		indio_dev->info = &tsl2563_info;
 	else
 		indio_dev->info = &tsl2563_info_no_irq;
+
 	if (client->irq) {
-		ret = request_threaded_irq(client->irq,
+		err = request_threaded_irq(client->irq,
 					   NULL,
 					   &tsl2563_event_handler,
 					   IRQF_TRIGGER_RISING | IRQF_ONESHOT,
 					   "tsl2563_event",
 					   indio_dev);
-		if (ret)
-			goto fail2;
+		if (err) {
+			dev_err(&client->dev, "irq request error %d\n", -err);
+			goto fail1;
+		}
 	}
+
 	err = tsl2563_configure(chip);
-	if (err)
-		goto fail3;
+	if (err) {
+		dev_err(&client->dev, "configure error %d\n", -err);
+		goto fail2;
+	}
 
 	INIT_DELAYED_WORK(&chip->poweroff_work, tsl2563_poweroff_work);
+
 	/* The interrupt cannot yet be enabled so this is fine without lock */
 	schedule_delayed_work(&chip->poweroff_work, 5 * HZ);
 
-	ret = iio_device_register(indio_dev);
-	if (ret)
+	err = iio_device_register(indio_dev);
+	if (err) {
+		dev_err(&client->dev, "iio registration error %d\n", -err);
 		goto fail3;
+	}
 
 	return 0;
+
 fail3:
+	cancel_delayed_work(&chip->poweroff_work);
+	flush_scheduled_work();
+fail2:
 	if (client->irq)
 		free_irq(client->irq, indio_dev);
-fail2:
-	iio_free_device(indio_dev);
 fail1:
-	kfree(chip);
+	iio_free_device(indio_dev);
 	return err;
 }
 
-- 
1.7.3.4

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