uio: Fix use-after-free in uio_open

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: uio: Fix use-after-free in uio_open core-1 core-2 ------------------------------------------------------- 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) ------------------------------------------------------- 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.

References

• https://git.kernel.org/stable/c/3174e0f7de1ba392dc191625da83df02d695b60c
• https://git.kernel.org/stable/c/e93da893d52d82d57fc0db2ca566024e0f26ff50
• https://git.kernel.org/stable/c/5e0be1229ae199ebb90b33102f74a0f22d152570
• https://git.kernel.org/stable/c/5cf604ee538ed0c467abe3b4cda5308a6398f0f7
• https://git.kernel.org/stable/c/17a8519cb359c3b483fb5c7367efa9a8a508bdea
• https://git.kernel.org/stable/c/35f102607054faafe78d2a6994b18d5d9d6e92ad
• https://git.kernel.org/stable/c/913205930da6213305616ac539447702eaa85e41
• https://git.kernel.org/stable/c/0c9ae0b8605078eafc3bea053cc78791e97ba2e2