[PATCH v5 1/5] iio: core: add read_avail_release_resource callback to fix race

Matteo Martelli
2024-10-21T12:56:27Z

Some iio drivers currently share an available info buffer that might be
changed while iio core prints it to sysfs. To avoid the buffer
corruption, add a release callback to let iio drivers allocate a copy of
the available info buffer and later free it in the release callback.
Such control is kept in the driver logic so that some driver that needs
a big available info buffer might also perform some check to keep the
copied buffer around in case no race has occurred.

Signed-off-by: Matteo Martelli <matteomartelli3@gmail.com>
---
drivers/iio/industrialio-core.c | 14 +++++++++++---
include/linux/iio/iio.h | 4 ++++
2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 6a6568d4a2cb3a3f63381d5a6f25a2881b3ba2ed..4aea9de9f15a4d70f9d02fb3d47df49eef8c8423 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -859,12 +859,20 @@ static ssize_t iio_read_channel_info_avail(struct device *dev,
return ret;
switch (ret) {
case IIO_AVAIL_LIST:
- return iio_format_avail_list(buf, vals, type, length);
+ ret = iio_format_avail_list(buf, vals, type, length);
+ break;
case IIO_AVAIL_RANGE:
- return iio_format_avail_range(buf, vals, type);
+ ret = iio_format_avail_range(buf, vals, type);
+ break;
default:
- return -EINVAL;
+ ret = -EINVAL;
}
+
+ if (indio_dev->info->read_avail_release_resource)
+ indio_dev->info->read_avail_release_resource(
+ indio_dev, this_attr->c, vals, this_attr->address);
+
+ return ret;
}

/**
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 3a9b57187a958d6e65c699cf7814df5bac9a99e3..03bb765670a0c5f0129fc677c3a4a4cb38f4dad1 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -491,6 +491,10 @@ struct iio_info {
int *length,
long mask);

+ void (*read_avail_release_resource)(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ const int *vals, long mask);
+
int (*write_raw)(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int val,

--
2.47.0