From 19833c40d0415d6fe4340b5b9c46239abbf718f6 Mon Sep 17 00:00:00 2001
From: Yang Yingliang <yangyingliang@huawei.com>
Date: Wed, 13 Oct 2021 11:05:32 +0800
Subject: [PATCH] iio: core: fix double free in iio_device_unregister_sysfs()
Git-commit: 19833c40d0415d6fe4340b5b9c46239abbf718f6
Patch-mainline: v5.16-rc1
References: git-fixes stable-5.14.19

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@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20211013030532.956133-1-yangyingliang@huawei.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/iio/industrialio-core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 48fda6a79076..3e1e86d987cc 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -1600,6 +1600,7 @@ static void iio_device_unregister_sysfs(struct iio_dev *indio_dev)
 	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)
-- 
2.26.2