i2c: Fix a potential use after free

[ 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>

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index cfbef70..8fb065c 100644 (file)
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2464,8 +2464,9 @@ 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);