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CVE-2023-54107 (GCVE-0-2023-54107)

Vulnerability from cvelistv5 – Published: 2025-12-24 13:06 – Updated: 2026-08-05 09:17
VLAI
Title
blk-cgroup: dropping parent refcount after pd_free_fn() is done
Summary
In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: dropping parent refcount after pd_free_fn() is done Some cgroup policies will access parent pd through child pd even after pd_offline_fn() is done. If pd_free_fn() for parent is called before child, then UAF can be triggered. Hence it's better to guarantee the order of pd_free_fn(). Currently refcount of parent blkg is dropped in __blkg_release(), which is before pd_free_fn() is called in blkg_free_work_fn() while blkg_free_work_fn() is called asynchronously. This patch make sure pd_free_fn() called from removing cgroup is ordered by delaying dropping parent refcount after calling pd_free_fn() for child. BTW, pd_free_fn() will also be called from blkcg_deactivate_policy() from deleting device, and following patches will guarantee the order.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d578c770c85233af592e54537f93f3831bde7e9a , < c7241babf0855d8a6180cd1743ff0ec34de40b4e (git)
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Linux Linux Affected: 5.18
Unaffected: 0 , < 5.18 (semver)
Unaffected: 6.3 , ≤ * (original_commit_for_fix)
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              "value": "AV:L - Triggering requires local cgroup filesystem operations (mkdir/rmdir of nested cgroups, writes to io.max/io.weight/io.latency) plus block I/O to populate blkgs. There is no remote or adjacent-network path into blk-cgroup teardown.\nAC:L - Although the UAF arises from unordered asynchronous work items and timers, the attacker controls both sides \u2014 building the nested blkcg hierarchy, choosing the tear-down order and timing, looping thousands of create/destroy cycles, and loading system_wq to widen the window while pd_free_fn sleeps (hrtimer_cancel, blk_put_queue). The iocost/throttle timers also fire on their own, so the window recurs without any condition outside attacker influence.\nPR:L - An unprivileged local account with a delegated cgroup v2 subtree suffices \u2014 standard systemd user slices and rootless/OCI containers grant mkdir/rmdir plus ownership of the non-root io.max, io.weight and io.latency files in cgroups the user creates, and bfq/blk-throttle policies are active without any privileged setup. No real root in the initial namespace is needed.\nUI:N - The attacker performs the entire sequence \u2014 cgroup creation, I/O generation, and rmdir \u2014 in its own process with no action by any other user.\nS:U - The corruption is confined to kernel heap objects managed by the same kernel security authority; no VM, hypervisor, or IOMMU boundary is crossed.\nC:H - The freed parent ioc_gq/throtl_grp/bfq_group lives in a general kmalloc cache, and __propagate_weights()/current_hweight() read child_active_sum, child_inuse_sum, active and inuse straight out of the reclaimed slot, with results observable via io.stat and scheduling behaviour. Heap grooming turns this into a controllable kernel-memory disclosure primitive.\nI:H - __propagate_weights() performs read-modify-write arithmetic directly on the freed parent object (parent-\u003echild_active_sum += ..., parent-\u003echild_inuse_sum += ...) with deltas derived from attacker-chosen io.weight values, and throtl_rb_erase() writes rb-tree pointers into the freed parent service queue. Sprayed into an attacker-chosen reclaimed object, this is a write primitive leading to control-flow hijack and privilege escalation.\nA:H - Use-after-free access and modification of freed slab memory reliably produces KASAN splats, rb-tree/slab corruption, and kernel oops or panic, and the sequence can be repeated at will to crash the machine."
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    "dateReserved": "2025-12-24T13:02:52.517Z",
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    "redhat_vex": {
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      "current_release_date": "2026-08-04T19:13:41+00:00",
      "cve": "CVE-2023-54107",
      "id": "CVE-2023-54107",
      "initial_release_date": "2023-01-01T00:00:00+00:00",
      "product_status:known_affected": "198",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel blk-cgroup: Use-after-free vulnerability leading to denial of service",
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      "cve": "CVE-2023-54107",
      "id": "CVE-2023-54107",
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      "source": "SUSE CSAF VEX",
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      "title": "SUSE CVE CVE-2023-54107",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2023-54107.json",
      "version": "19"
    }
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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