mfd: wm831x-auxadc: Prevent use after free in wm831x_auxadc_read_irq()

stable inclusion
from stable-5.10.20
commit b1b904813755d825eff31222d2d24b05638c0c52
bugzilla: 50608

--------------------------------

[ Upstream commit 26783d74 ]

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: 78bb3688 ("mfd: Support multiple active WM831x AUXADC conversions")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NCharles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/mfd/wm831x-auxadc.c

@@ -93,11 +93,10 @@ 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);