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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jeremy Cline <jeremy@jcline.org>,
        Hans de Goede <hdegoede@redhat.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Stable@vger.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>
Subject: [PATCH 5.12 092/700] iio: accel: bmc150: Fix dereferencing the wrong pointer in bmc150_get/set_second_device
Date:   Mon, 12 Jul 2021 08:02:55 +0200
Message-Id: <20210712060937.764803550@linuxfoundation.org>
In-Reply-To: <20210712060924.797321836@linuxfoundation.org>
References: <20210712060924.797321836@linuxfoundation.org>
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From: Hans de Goede <hdegoede@redhat.com>

commit f2bf22dc9ea8ead180fc0221874bd556bf1d2685 upstream.

The drvdata for iio-parent devices points to the struct iio_dev for
the iio-device. So by directly casting the return from i2c_get_clientdata()
to struct bmc150_accel_data * the code was ending up storing the second_dev
pointer in (and retrieving it from) some semi-random offset inside
struct iio_dev, rather then storing it in the second_dev member of the
bmc150_accel_data struct.

Fix the code to get the struct bmc150_accel_data * pointer to call
iio_priv() on the struct iio_dev * returned by i2c_get_clientdata(),
so that the correct pointer gets dereferenced.

This fixes the following oops on rmmod, caused by trying to
dereference the wrong return of bmc150_get_second_device():

[  238.980737] BUG: unable to handle page fault for address: 0000000000004710
[  238.980755] #PF: supervisor read access in kernel mode
[  238.980760] #PF: error_code(0x0000) - not-present page
...
[  238.980841]  i2c_unregister_device.part.0+0x19/0x60
[  238.980856]  0xffffffffc0815016
[  238.980863]  i2c_device_remove+0x25/0xb0
[  238.980869]  __device_release_driver+0x180/0x240
[  238.980876]  driver_detach+0xd4/0x120
[  238.980882]  bus_remove_driver+0x5b/0xd0
[  238.980888]  i2c_del_driver+0x44/0x70

While at it also remove the now no longer sensible checks for data
being NULL, iio_priv never returns NULL for an iio_dev with non 0
sized private-data.

Fixes: 5bfb3a4bd8f6 ("iio: accel: bmc150: Check for a second ACPI device for BOSC0200")
Cc: Jeremy Cline <jeremy@jcline.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/iio/accel/bmc150-accel-core.c |   10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

--- a/drivers/iio/accel/bmc150-accel-core.c
+++ b/drivers/iio/accel/bmc150-accel-core.c
@@ -1805,10 +1805,7 @@ EXPORT_SYMBOL_GPL(bmc150_accel_core_prob
 
 struct i2c_client *bmc150_get_second_device(struct i2c_client *client)
 {
-	struct bmc150_accel_data *data = i2c_get_clientdata(client);
-
-	if (!data)
-		return NULL;
+	struct bmc150_accel_data *data = iio_priv(i2c_get_clientdata(client));
 
 	return data->second_device;
 }
@@ -1816,10 +1813,9 @@ EXPORT_SYMBOL_GPL(bmc150_get_second_devi
 
 void bmc150_set_second_device(struct i2c_client *client)
 {
-	struct bmc150_accel_data *data = i2c_get_clientdata(client);
+	struct bmc150_accel_data *data = iio_priv(i2c_get_clientdata(client));
 
-	if (data)
-		data->second_device = client;
+	data->second_device = client;
 }
 EXPORT_SYMBOL_GPL(bmc150_set_second_device);