[PATCH 5.14 152/849] iio: core: fix double free in iio_device_unregister_sysfs()

[Greg Kroah-Hartman]

From: Yang Yingliang <yangyingliang@xxxxxxxxxx>

commit 19833c40d0415d6fe4340b5b9c46239abbf718f6 upstream.

I got the double free report:

BUG: KASAN: double-free or invalid-free in kfree+0xce/0x390
 iio_device_unregister_sysfs+0x108/0x13b [industrialio]
 iio_dev_release+0x9e/0x10e [industrialio]
 device_release+0xa5/0x240

If __iio_device_register() fails, iio_dev_opaque->groups will be freed
in error path in iio_device_unregister_sysfs(), then iio_dev_release()
will call iio_device_unregister_sysfs() again, it causes double free.
Set iio_dev_opaque->groups to NULL when it's freed to fix this double free.

Not this is a local work around for a more general mess around life time
management that will get cleaned up and should make this handling
unnecesarry.

Fixes: 32f171724e5c ("iio: core: rework iio device group creation")
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Reviewed-by: Alexandru Ardelean <ardeleanalex@xxxxxxxxx>
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211013030532.956133-1-yangyingliang@xxxxxxxxxx
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/iio/industrialio-core.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -1597,6 +1597,7 @@ static void iio_device_unregister_sysfs(
 	kfree(iio_dev_opaque->chan_attr_group.attrs);
 	iio_dev_opaque->chan_attr_group.attrs = NULL;
 	kfree(iio_dev_opaque->groups);
+	iio_dev_opaque->groups = NULL;
 }
 
 static void iio_dev_release(struct device *device)