CVE-2023-54019 sched/psi: use kernfs polling functions for PSI trigger polling

What is CVE-2023-54019?

CVE-2023-54019 is a high-severity use after free vulnerability in Linux, published on 24 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

sched/psi: use kernfs polling functions for PSI trigger polling

Destroying psi trigger in cgroup_file_release causes UAF issues when a cgroup is removed from under a polling process. This is happening because cgroup removal causes a call to cgroup_file_release while the actual file is still alive. Destroying the trigger at this point would also destroy its waitqueue head and if there is still a polling process on that file accessing the waitqueue, it will step on the freed pointer:

do_select vfs_poll do_rmdir cgroup_rmdir kernfs_drain_open_files cgroup_file_release cgroup_pressure_release psi_trigger_destroy wake_up_pollfree(&t->event_wait) // vfs_poll is unblocked synchronize_rcu kfree(t) poll_freewait -> UAF access to the trigger's waitqueue head

Patch [1] fixed this issue for epoll() case using wake_up_pollfree(), however the same issue exists for synchronous poll() case. The root cause of this issue is that the lifecycles of the psi trigger's waitqueue and of the file associated with the trigger are different. Fix this by using kernfs_generic_poll function when polling on cgroup-specific psi triggers. It internally uses kernfs_open_node->poll waitqueue head with its lifecycle tied to the file's lifecycle. This also renders the fix in [1] obsolete, so revert it.

[1] commit c2dbe32d5db5 ("sched/psi: Fix use-after-free in ep_remove_wait_queue()")

Which versions are affected by CVE-2023-54019?

How do I fix CVE-2023-54019?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2023-54019 being exploited?

There is no known exploitation of CVE-2023-54019 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2023-54019, DEBIAN-CVE-2023-54019, GHSA-j7pj-g3hv-5hcw, ROOT-OS-DEBIAN-11-CVE-2023-54019, ROOT-OS-UBUNTU-2204-CVE-2023-54019, UBUNTU-CVE-2023-54019.