On 17/03/14 08:01, Krzysztof Kozlowski wrote:
Hi,
On Sat, 2014-03-15 at 16:24 +0000, Jonathan Cameron wrote:
On 06/03/14 09:33, Krzysztof Kozlowski wrote:
During probe the driver allocates dummy I2C devices (i2c_new_dummy())
but they aren't unregistered during driver remove or probe failure.
Additionally driver does not check the return value of i2c_new_dummy().
In case of error (i2c_new_device(): memory allocation failure or I2C
address cannot be used) this function returns NULL which is later
dereferenced by i2c_smbus_{read,write}_data() functions.
Fix issues by properly checking for i2c_new_dummy() return value and
unregistering I2C devices on driver remove or probe failure.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
Good catch, but the error path needs more care.
---
drivers/iio/light/cm36651.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/drivers/iio/light/cm36651.c b/drivers/iio/light/cm36651.c
index a45e07492db3..e7e9a597159f 100644
--- a/drivers/iio/light/cm36651.c
+++ b/drivers/iio/light/cm36651.c
@@ -653,6 +653,11 @@ static int cm36651_probe(struct i2c_client *client,
cm36651->ps_client = i2c_new_dummy(client->adapter,
CM36651_I2C_ADDR_PS);
cm36651->ara_client = i2c_new_dummy(client->adapter, CM36651_ARA);
+ if (!cm36651->ps_client || !cm36651->ara_client) {
+ dev_err(&client->dev, "%s: new i2c device failed\n", __func__);
+ ret = -ENODEV;
+ goto error_i2c_unregister;
+ }
The two failures need to be handled independently as we only want to unregister
those that succeeded. i2c_new_dummy will not return an error and leave a device
registered. This is particularly true given the first thing that i2c_unregister_device
does is to derefence the client pointer. That will cause a segfault if you do it
for NULL as here.
Where the segfault would occur? If i2c_new_dummy fails then
i2c_unregister_device() will be called only on NON-null values:
+error_i2c_unregister:
+ if (cm36651->ps_client)
+ i2c_unregister_device(cm36651->ps_client);
+ if (cm36651->ara_client)
+ i2c_unregister_device(cm36651->ara_client);
If probe() succeeds (both i2c_new_dummy return proper pointer) then
remove() will unregister two i2c devices.
Oops, I missed that. Still, the form of this is unusual so please
change it to the more conventional option of a goto per error rather
than grouping them. That will also allow you to drop the null checks
below leading to a more obviously correct error path.
mutex_init(&cm36651->lock);
indio_dev->dev.parent = &client->dev;
indio_dev->channels = cm36651_channels;
@@ -687,6 +692,11 @@ error_free_irq:
free_irq(client->irq, indio_dev);
error_disable_reg:
regulator_disable(cm36651->vled_reg);
+error_i2c_unregister:
+ if (cm36651->ps_client)
+ i2c_unregister_device(cm36651->ps_client);
+ if (cm36651->ara_client)
+ i2c_unregister_device(cm36651->ara_client);
return ret;
}
@@ -698,6 +708,8 @@ static int cm36651_remove(struct i2c_client *client)
iio_device_unregister(indio_dev);
regulator_disable(cm36651->vled_reg);
free_irq(client->irq, indio_dev);
+ i2c_unregister_device(cm36651->ps_client);
+ i2c_unregister_device(cm36651->ara_client);
Good catch.
return 0;
}
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