linux-kernel - [PATCH] s390: cio: fix two use-after-free bugs in device.c

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Date:   Fri, 20 Nov 2020 15:48:49 +0800
From:   Qinglang Miao <miaoqinglang@...wei.com>
To:     Vineeth Vijayan <vneethv@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
CC:     <linux-s390@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Qinglang Miao" <miaoqinglang@...wei.com>
Subject: [PATCH] s390: cio: fix two use-after-free bugs in device.c

put_device calls release function which do kfree() inside.
So following use of sch&cdev would cause use-after-free bugs.

Fix these by simply adjusting the position of put_device.

Fixes: 37db8985b211 ("s390/cio: add basic protected virtualization support")
Fixes: 74bd0d859dc3 ("s390/cio: fix unlocked access of online member")
Reported-by: Hulk Robot <hulkci@...wei.com>
Signed-off-by: Qinglang Miao <miaoqinglang@...wei.com>
---
 drivers/s390/cio/device.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index b29fe8d50..69492417b 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1664,10 +1664,10 @@ void __init ccw_device_destroy_console(struct ccw_device *cdev)
 	struct io_subchannel_private *io_priv = to_io_private(sch);
 
 	set_io_private(sch, NULL);
-	put_device(&sch->dev);
-	put_device(&cdev->dev);
 	dma_free_coherent(&sch->dev, sizeof(*io_priv->dma_area),
 			  io_priv->dma_area, io_priv->dma_area_dma);
+	put_device(&sch->dev);
+	put_device(&cdev->dev);
 	kfree(io_priv);
 }
 
@@ -1774,8 +1774,8 @@ static int ccw_device_remove(struct device *dev)
 				      ret, cdev->private->dev_id.ssid,
 				      cdev->private->dev_id.devno);
 		/* Give up reference obtained in ccw_device_set_online(). */
-		put_device(&cdev->dev);
 		spin_lock_irq(cdev->ccwlock);
+		put_device(&cdev->dev);
 	}
 	ccw_device_set_timeout(cdev, 0);
 	cdev->drv = NULL;
-- 
2.23.0