linux-kernel - [PATCH 4.9 032/116] power: supply: ltc2941-battery-gauge: fix use-after-free

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Date:   Thu, 13 Feb 2020 07:19:36 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sven Van Asbroeck <TheSven73@...il.com>,
        Sebastian Reichel <sebastian.reichel@...labora.com>
Subject: [PATCH 4.9 032/116] power: supply: ltc2941-battery-gauge: fix use-after-free

From: Sven Van Asbroeck <thesven73@...il.com>

commit a60ec78d306c6548d4adbc7918b587a723c555cc upstream.

This driver's remove path calls cancel_delayed_work().
However, that function does not wait until the work function
finishes. This could mean that the work function is still
running after the driver's remove function has finished,
which would result in a use-after-free.

Fix by calling cancel_delayed_work_sync(), which ensures that
that the work is properly cancelled, no longer running, and
unable to re-schedule itself.

This issue was detected with the help of Coccinelle.

Cc: stable <stable@...r.kernel.org>
Signed-off-by: Sven Van Asbroeck <TheSven73@...il.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/power/supply/ltc2941-battery-gauge.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/power/supply/ltc2941-battery-gauge.c
+++ b/drivers/power/supply/ltc2941-battery-gauge.c
@@ -364,7 +364,7 @@ static int ltc294x_i2c_remove(struct i2c
 {
 	struct ltc294x_info *info = i2c_get_clientdata(client);
 
-	cancel_delayed_work(&info->work);
+	cancel_delayed_work_sync(&info->work);
 	power_supply_unregister(info->supply);
 	return 0;
 }