linux-kernel - [PATCH] mfd: wm831x-auxadc: Prevent use after free in wm831x_auxadc_read

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Date:   Mon, 14 Dec 2020 14:59:10 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Mark Brown <broonie@...nsource.wolfsonmicro.com>,
        Samuel Ortiz <sameo@...ux.intel.com>,
        patches@...nsource.cirrus.com, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] mfd: wm831x-auxadc: Prevent use after free in
 wm831x_auxadc_read_irq()

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@...cle.com>
---
 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 8a7cc0f86958..65b98f3fbd92 100644
--- a/drivers/mfd/wm831x-auxadc.c
+++ b/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);
-- 
2.29.2