linux-kernel - [PATCH] hwmon: (xgene) Fix use after free bug in xgene_hwmon

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Date:   Fri, 10 Mar 2023 16:40:07 +0800
From:   Zheng Wang <zyytlz.wz@....com>
To:     jdelvare@...e.com
Cc:     linux@...ck-us.net, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, hackerzheng666@...il.com,
        1395428693sheep@...il.com, alex000young@...il.com,
        Zheng Wang <zyytlz.wz@....com>
Subject: [PATCH] hwmon: (xgene) Fix use after free bug in xgene_hwmon_remove due to race condition

In xgene_hwmon_probe, &ctx->workq is bound with
xgene_hwmon_evt_work. Then it will be started.

If we remove the driver which will call
xgene_hwmon_remove to make cleanup, there may
be a unfinished work.

The possiblesequence is as follows:

Fix it by finishing the work before cleanup in the
xgene_hwmon_remove

CPU0                  CPU1

                    |xgene_hwmon_evt_work
xgene_hwmon_remove   |
kfifo_free(&ctx->async_msg_fifo);|
                    |
                    |kfifo_out_spinlocked
                    |//use &ctx->async_msg_fifo
Fixes: 2ca492e22cb7 ("hwmon: (xgene) Fix crash when alarm occurs before driver probe")
Signed-off-by: Zheng Wang <zyytlz.wz@....com>
---
 drivers/hwmon/xgene-hwmon.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hwmon/xgene-hwmon.c b/drivers/hwmon/xgene-hwmon.c
index 5cde837bfd09..d1abea49f01b 100644
--- a/drivers/hwmon/xgene-hwmon.c
+++ b/drivers/hwmon/xgene-hwmon.c
@@ -761,6 +761,7 @@ static int xgene_hwmon_remove(struct platform_device *pdev)
 {
 	struct xgene_hwmon_dev *ctx = platform_get_drvdata(pdev);
 
+	cancel_work_sync(&ctx->workq);
 	hwmon_device_unregister(ctx->hwmon_dev);
 	kfifo_free(&ctx->async_msg_fifo);
 	if (acpi_disabled)
-- 
2.25.1