[PATCH 3.2 141/221] iio: core: Fix double free.

Ben Hutchings
2015-05-05T01:25:58Z

From: Martin Fuzzey <mfuzzey@parkeon.com>

commit c1b03ab5e886760bdd38c9c7a27af149046ffe01 upstream.

When an error occurred during event registration memory was freed twice
resulting in kernel memory corruption and a crash in unrelated code.

The problem was caused by
iio_device_unregister_eventset()
iio_device_unregister_sysfs()

being called twice, once on the error path and then
again via iio_dev_release().

Fix this by making these two functions idempotent so they
may be called multiple times.

The problem was observed before applying
78b33216 iio:core: Handle error when mask type is not separate

Signed-off-by: Martin Fuzzey <mfuzzey@parkeon.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
[bwh: Backported to 3.2:
- Adjust filenames, context
- Drop inapplicable change to iio_free_chan_devattr_list()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/drivers/staging/iio/industrialio-core.c
+++ b/drivers/staging/iio/industrialio-core.c
@@ -711,6 +711,7 @@ static void iio_device_unregister_sysfs(
iio_device_remove_and_free_read_attr(indio_dev, p);
}
kfree(indio_dev->chan_attr_group.attrs);
+ indio_dev->chan_attr_group.attrs = NULL;
}

static const char * const iio_ev_type_text[] = {
@@ -986,6 +987,7 @@ static int iio_device_register_eventset(
error_free_setup_event_lines:
__iio_remove_event_config_attrs(indio_dev);
kfree(indio_dev->event_interface);
+ indio_dev->event_interface = NULL;
error_ret:

return ret;