Use After Free Affecting kernel-tools package, versions <0:4.18.0-477.70.1.el8_8

Note: Versions mentioned in the description apply only to the upstream kernel-tools package and not the kernel-tools package as distributed by RHEL. See How to fix? for RHEL:8 relevant fixed versions and status.

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

gfs2: Fix potential glock use-after-free on unmount

When a DLM lockspace is released and there ares still locks in that lockspace, DLM will unlock those locks automatically. Commit fb6791d100d1b started exploiting this behavior to speed up filesystem unmount: gfs2 would simply free glocks it didn't want to unlock and then release the lockspace. This didn't take the bast callbacks for asynchronous lock contention notifications into account, which remain active until until a lock is unlocked or its lockspace is released.

To prevent those callbacks from accessing deallocated objects, put the glocks that should not be unlocked on the sd_dead_glocks list, release the lockspace, and only then free those glocks.

As an additional measure, ignore unexpected ast and bast callbacks if the receiving glock is dead.

• https://access.redhat.com/security/cve/CVE-2024-38570
• https://git.kernel.org/stable/c/0636b34b44589b142700ac137b5f69802cfe2e37
• https://git.kernel.org/stable/c/501cd8fabf621d10bd4893e37f6ce6c20523c8ca
• https://git.kernel.org/stable/c/d98779e687726d8f8860f1c54b5687eec5f63a73
• https://git.kernel.org/stable/c/e42e8a24d7f02d28763d16ca7ec5fc6d1f142af0