linux-kernel - [PATCH] media: msi2500: fix UAF in the msi2500

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Date:   Wed, 17 Nov 2021 00:32:07 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Antti Palosaari <crope@....fi>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Dongliang Mu <mudongliangabcd@...il.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] media: msi2500: fix UAF in the msi2500_disconnect

In msi2500_probe, it invokes spi_alloc_master to allocate master
controller and spi_register_master to register master controller.
Then in msi2500_disconnect, it calls spi_unregister_master to unregister
the master controller. And in spi_unregister_master, it calls put_device
to decrease the refcount and the device object will be freed then. As a
result, the dereference of dev->lock will cause a use-after-free bug.

Fix it by changing spi_alloc_master to devm_spi_alloc_master, and
removing spi_master_put in the error handling code.

Note that this patch can prevent UAF occurring any more

Fixes: fd8b5f502929 ("msi2500: move msi3101 out of staging and rename")
Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
---
 drivers/media/usb/msi2500/msi2500.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/media/usb/msi2500/msi2500.c b/drivers/media/usb/msi2500/msi2500.c
index 71de6b4c4e4c..64c3ec9f1d0c 100644
--- a/drivers/media/usb/msi2500/msi2500.c
+++ b/drivers/media/usb/msi2500/msi2500.c
@@ -1220,7 +1220,7 @@ static int msi2500_probe(struct usb_interface *intf,
 	}
 
 	/* SPI master adapter */
-	master = spi_alloc_master(dev->dev, 0);
+	master = devm_spi_alloc_master(dev->dev, 0);
 	if (master == NULL) {
 		ret = -ENOMEM;
 		goto err_unregister_v4l2_dev;
@@ -1233,7 +1233,6 @@ static int msi2500_probe(struct usb_interface *intf,
 	spi_master_set_devdata(master, dev);
 	ret = spi_register_master(master);
 	if (ret) {
-		spi_master_put(master);
 		goto err_unregister_v4l2_dev;
 	}
 
-- 
2.25.1