Use After Free Affecting kernel-rt-kvm package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-kvm package and not the kernel-rt-kvm package as distributed by Centos. See How to fix? for Centos:7 relevant fixed versions and status.

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.

• https://access.redhat.com/security/cve/CVE-2023-52439
• https://git.kernel.org/stable/c/0c9ae0b8605078eafc3bea053cc78791e97ba2e2
• https://git.kernel.org/stable/c/17a8519cb359c3b483fb5c7367efa9a8a508bdea
• https://git.kernel.org/stable/c/3174e0f7de1ba392dc191625da83df02d695b60c
• https://git.kernel.org/stable/c/35f102607054faafe78d2a6994b18d5d9d6e92ad
• https://git.kernel.org/stable/c/5cf604ee538ed0c467abe3b4cda5308a6398f0f7
• https://git.kernel.org/stable/c/5e0be1229ae199ebb90b33102f74a0f22d152570
• https://git.kernel.org/stable/c/913205930da6213305616ac539447702eaa85e41
• https://git.kernel.org/stable/c/e93da893d52d82d57fc0db2ca566024e0f26ff50
• https://lists.debian.org/debian-lts-announce/2024/06/msg00016.html