iio:buffer: Add proper locking for iio_update_buffers()

We need to make sure that in-kernel users of iio_update_buffers() do not race
against each other or against unregistration of the device. So we need to take
both the mlock and the info_exist_lock when calling iio_update_buffers() from a
in-kernel consumer.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 5a46c57..d6a5455 100644 (file)
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -509,7 +509,7 @@ void iio_disable_all_buffers(struct iio_dev *indio_dev)
                indio_dev->setup_ops->postdisable(indio_dev);
 }
 
-int iio_update_buffers(struct iio_dev *indio_dev,
+static int __iio_update_buffers(struct iio_dev *indio_dev,
                       struct iio_buffer *insert_buffer,
                       struct iio_buffer *remove_buffer)
 {
@@ -674,6 +674,29 @@ error_ret:
 
        return ret;
 }
+
+int iio_update_buffers(struct iio_dev *indio_dev,
+                      struct iio_buffer *insert_buffer,
+                      struct iio_buffer *remove_buffer)
+{
+       int ret;
+
+       mutex_lock(&indio_dev->info_exist_lock);
+       mutex_lock(&indio_dev->mlock);
+
+       if (indio_dev->info == NULL) {
+               ret = -ENODEV;
+               goto out_unlock;
+       }
+
+       ret = __iio_update_buffers(indio_dev, insert_buffer, remove_buffer);
+
+out_unlock:
+       mutex_unlock(&indio_dev->mlock);
+       mutex_unlock(&indio_dev->info_exist_lock);
+
+       return ret;
+}
 EXPORT_SYMBOL_GPL(iio_update_buffers);
 
 ssize_t iio_buffer_store_enable(struct device *dev,
@@ -699,10 +722,10 @@ ssize_t iio_buffer_store_enable(struct device *dev,
                goto done;
 
        if (requested_state)
-               ret = iio_update_buffers(indio_dev,
+               ret = __iio_update_buffers(indio_dev,
                                         indio_dev->buffer, NULL);
        else
-               ret = iio_update_buffers(indio_dev,
+               ret = __iio_update_buffers(indio_dev,
                                         NULL, indio_dev->buffer);
 
        if (ret < 0)