[PATCH 4.19 072/287] i2c: Fix a potential use after free

[Greg Kroah-Hartman]

From: Xu Wang <vulab@xxxxxxxxxxx>

[ 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@xxxxxxxxxxx>
[wsa: added comment to the code, added Fixes tag]
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 2a43f4e46af0..9079be0d51d1 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2273,8 +2273,9 @@ 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