[PATCH 4.9 067/134] mfd: wm831x-auxadc: Prevent use after free in wm831x_auxadc_read_irq()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit 26783d74cc6a440ee3ef9836a008a697981013d0 ]

The "req" struct is always added to the "wm831x->auxadc_pending" list,
but it's only removed from the list on the success path.  If a failure
occurs then the "req" struct is freed but it's still on the list,
leading to a use after free.

Fixes: 78bb3688ea18 ("mfd: Support multiple active WM831x AUXADC conversions")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Acked-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/mfd/wm831x-auxadc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/mfd/wm831x-auxadc.c b/drivers/mfd/wm831x-auxadc.c
index fd789d2eb0f52..9f7ae1e1ebcd6 100644
--- a/drivers/mfd/wm831x-auxadc.c
+++ b/drivers/mfd/wm831x-auxadc.c
@@ -98,11 +98,10 @@ static int wm831x_auxadc_read_irq(struct wm831x *wm831x,
 	wait_for_completion_timeout(&req->done, msecs_to_jiffies(500));
 
 	mutex_lock(&wm831x->auxadc_lock);
-
-	list_del(&req->list);
 	ret = req->val;
 
 out:
+	list_del(&req->list);
 	mutex_unlock(&wm831x->auxadc_lock);
 
 	kfree(req);
-- 
2.27.0