linux-kernel - [PATCH 5.17 0030/1126] iio: accel: mma8452: use the correct logic to get mma8452

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Date:   Tue,  5 Apr 2022 09:12:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Haibo Chen <haibo.chen@....com>,
        Martin Kepplinger <martink@...teo.de>, Stable@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH 5.17 0030/1126] iio: accel: mma8452: use the correct logic to get mma8452_data

From: Haibo Chen <haibo.chen@....com>

commit c87b7b12f48db86ac9909894f4dc0107d7df6375 upstream.

The original logic to get mma8452_data is wrong, the *dev point to
the device belong to iio_dev. we can't use this dev to find the
correct i2c_client. The original logic happen to work because it
finally use dev->driver_data to get iio_dev. Here use the API
to_i2c_client() is wrong and make reader confuse. To correct the
logic, it should be like this

  struct mma8452_data *data = iio_priv(dev_get_drvdata(dev));

But after commit 8b7651f25962 ("iio: iio_device_alloc(): Remove
unnecessary self drvdata"), the upper logic also can't work.
When try to show the avialable scale in userspace, will meet kernel
dump, kernel handle NULL pointer dereference.

So use dev_to_iio_dev() to correct the logic.

Dual fixes tags as the second reflects when the bug was exposed, whilst
the first reflects when the original bug was introduced.

Fixes: c3cdd6e48e35 ("iio: mma8452: refactor for seperating chip specific data")
Fixes: 8b7651f25962 ("iio: iio_device_alloc(): Remove unnecessary self drvdata")
Signed-off-by: Haibo Chen <haibo.chen@....com>
Reviewed-by: Martin Kepplinger <martink@...teo.de>
Cc: <Stable@...r.kernel.org>
Link: https://lore.kernel.org/r/1645497741-5402-1-git-send-email-haibo.chen@nxp.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/iio/accel/mma8452.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/iio/accel/mma8452.c
+++ b/drivers/iio/accel/mma8452.c
@@ -379,8 +379,8 @@ static ssize_t mma8452_show_scale_avail(
 					struct device_attribute *attr,
 					char *buf)
 {
-	struct mma8452_data *data = iio_priv(i2c_get_clientdata(
-					     to_i2c_client(dev)));
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mma8452_data *data = iio_priv(indio_dev);

 	return mma8452_show_int_plus_micros(buf, data->chip_info->mma_scales,
 		ARRAY_SIZE(data->chip_info->mma_scales));