[PATCH 5.18 0340/1095] i2c: Fix a potential use after free

Greg Kroah-Hartman
2022-08-15T21:05:03Z

From: Xu Wang <vulab@iscas.ac.cn>

[ Upstream commit e4c72c06c367758a14f227c847f9d623f1994ecf ]

Free the adap structure only after we are done using it.
This patch just moves the put_device() down a bit to avoid the
use after free.

Fixes: 611e12ea0f12 ("i2c: core: manage i2c bus device refcount in i2c_[get|put]_adapter")
Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
[wsa: added comment to the code, added Fixes tag]
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/i2c/i2c-core-base.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index d43db2c3876e..19a317fdcf5b 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2467,8 +2467,9 @@ void i2c_put_adapter(struct i2c_adapter *adap)
if (!adap)
return;

- put_device(&adap->dev);
module_put(adap->owner);
+ /* Should be last, otherwise we risk use-after-free with 'adap' */
+ put_device(&adap->dev);
}
EXPORT_SYMBOL(i2c_put_adapter);

--
2.35.1