CVE-2023-52439

In the Linux kernel, the following vulnerability has been resolved:

uio: Fix use-after-free in uio_open

core-1 core-2

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uio_unregister_device uio_open

idev = idr_find()

device_unregister(&idev->dev)

put_device(&idev->dev)

uio_device_release

get_device(&idev->dev)

kfree(idev)

uio_free_minor(minor)

uio_release

put_device(&idev->dev)

kfree(idev)

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In the core-1 uio_unregister_device(), the device_unregister will kfree

idev when the idev->dev kobject ref is 1. But after core-1

device_unregister, put_device and before doing kfree, the core-2 may

get_device. Then:

1. After core-1 kfree idev, the core-2 will do use-after-free for idev.

2. When core-2 do uio_release and put_device, the idev will be double

freed.

To address this issue, we can get idev atomic & inc idev reference with

minor_lock.