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CVE Record

CVE-2023-52707: sched/psi: Fix use-after-free in ep_remove_wait_queue()

In the Linux kernel, the following vulnerability has been resolved: sched/psi: Fix use-after-free in ep_remove_wait_queue() If a non-root cgroup gets removed when there is a thread that registered trigger and is polling on a pressure file within the cgroup, the polling waitqueue gets freed in the following path: do_rmdir cgroup_rmdir kernfs_drain_open_files cgroup_file_release cgroup_pressure_release psi_trigger_destroy However, the polling thread still has a reference to the pressure file and will access the freed waitqueue when the file is closed or upon exit: fput ep_eventpoll_release ep_free ep_remove_wait_queue remove_wait_queue This results in use-after-free as pasted below. The fundamental problem here is that cgroup_file_release() (and consequently waitqueue's lifetime) is not tied to the file's real lifetime. Using wake_up_pollfree() here might be less than ideal, but it is in line with the comment at commit 42288cb44c4b ("wait: add wake_up_pollfree()") since the waitqueue's lifetime is not tied to file's one and can be considered as another special case. While this would be fixable by somehow making cgroup_file_release() be tied to the fput(), it would require sizable refactoring at cgroups or higher layer which might be more justifiable if we identify more cases like this. BUG: KASAN: use-after-free in _raw_spin_lock_irqsave+0x60/0xc0 Write of size 4 at addr ffff88810e625328 by task a.out/4404 CPU: 19 PID: 4404 Comm: a.out Not tainted 6.2.0-rc6 #38 Hardware name: Amazon EC2 c5a.8xlarge/, BIOS 1.0 10/16/2017 Call Trace: <TASK> dump_stack_lvl+0x73/0xa0 print_report+0x16c/0x4e0 kasan_report+0xc3/0xf0 kasan_check_range+0x2d2/0x310 _raw_spin_lock_irqsave+0x60/0xc0 remove_wait_queue+0x1a/0xa0 ep_free+0x12c/0x170 ep_eventpoll_release+0x26/0x30 __fput+0x202/0x400 task_work_run+0x11d/0x170 do_exit+0x495/0x1130 do_group_exit+0x100/0x100 get_signal+0xd67/0xde0 arch_do_signal_or_restart+0x2a/0x2b0 exit_to_user_mode_prepare+0x94/0x100 syscall_exit_to_user_mode+0x20/0x40 do_syscall_64+0x52/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd </TASK> Allocated by task 4404: kasan_set_track+0x3d/0x60 __kasan_kmalloc+0x85/0x90 psi_trigger_create+0x113/0x3e0 pressure_write+0x146/0x2e0 cgroup_file_write+0x11c/0x250 kernfs_fop_write_iter+0x186/0x220 vfs_write+0x3d8/0x5c0 ksys_write+0x90/0x110 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Freed by task 4407: kasan_set_track+0x3d/0x60 kasan_save_free_info+0x27/0x40 ____kasan_slab_free+0x11d/0x170 slab_free_freelist_hook+0x87/0x150 __kmem_cache_free+0xcb/0x180 psi_trigger_destroy+0x2e8/0x310 cgroup_file_release+0x4f/0xb0 kernfs_drain_open_files+0x165/0x1f0 kernfs_drain+0x162/0x1a0 __kernfs_remove+0x1fb/0x310 kernfs_remove_by_name_ns+0x95/0xe0 cgroup_addrm_files+0x67f/0x700 cgroup_destroy_locked+0x283/0x3c0 cgroup_rmdir+0x29/0x100 kernfs_iop_rmdir+0xd1/0x140 vfs_rmdir+0xfe/0x240 do_rmdir+0x13d/0x280 __x64_sys_rmdir+0x2c/0x30 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2023-52707 is a Linux kernel memory safety bug in cgroup pressure monitoring. Under specific local conditions, removing a non-root cgroup while another thread is polling its pressure file can cause a use-after-free. The public record shows kernel fixes, but no CVSS score and no evidence of active exploitation.

Executive priority

Treat as a normal-to-elevated Linux kernel patching item. Escalate priority for container platforms or shared Linux environments because the vulnerable path is local but kernel-level. No source provided confirms exploitation in the wild.

Technical view

The bug is in sched/psi handling around ep_remove_wait_queue(). cgroup_file_release() can free a polling waitqueue before the file’s real lifetime ends, so later eventpoll cleanup can access freed memory. The kernel fix uses wake_up_pollfree() for this special lifetime mismatch. The report includes a KASAN use-after-free trace on Linux 6.2.0-rc6.

Likely exposure

Exposure is most relevant to Linux systems using cgroups and PSI pressure files, especially container or multi-tenant hosts. The CVE record lists Linux kernel versions beginning at 5.2 with stable-branch fixes referenced. Exact exposure should be checked against the running kernel and distribution backports.

Exploitation context

The described condition requires local interaction with cgroups and polling of pressure files. Sources do not state remote exploitability, privilege escalation, public exploit availability, or active exploitation. It is not listed as CISA KEV in the provided bundle.

Researcher notes

The source bundle lacks CVSS, CWE, and detailed distro mapping. The affected-version data appears branch-oriented and should be reconciled with upstream stable commits and vendor backports. Avoid assuming exploitability beyond the documented use-after-free trigger and KASAN trace.

Mitigation direction

  • Update to a kernel containing the referenced stable fixes or your distribution’s backport.
  • Prioritize container hosts, multi-tenant Linux systems, and systems exposing cgroup management to untrusted users.
  • Check vendor advisories for package-specific fixed versions and reboot requirements.
  • If patching is delayed, reduce unnecessary untrusted access to cgroup management where operationally feasible.

Validation and detection

  • Inventory running kernel versions across Linux hosts.
  • Confirm whether the applicable stable commit or distribution backport is present.
  • Review vendor kernel changelogs for CVE-2023-52707 or the referenced sched/psi fix.
  • Identify hosts using cgroups and PSI pressure monitoring in containerized workloads.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2023-52707 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux0e94682b73bfa6c44c98af7a26771c9c08c055d5, 0e94682b73bfa6c44c98af7a26771c9c08c055d5, 0e94682b73bfa6c44c98af7a26771c9c08c055d5, 0e94682b73bfa6c44c98af7a26771c9c08c055d5, 0e94682b73bfa6c44c98af7a26771c9c08c055d5unaffected
LinuxLinux5.2, 0, 5.4.232, 5.10.169, 5.15.95, 6.1.13, 6.2affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.