CVE-2024-49573 (GCVE-0-2024-49573)

Vulnerability from cvelistv5 – Published: 2025-01-11 12:35 – Updated: 2026-08-05 11:40
VLAI
Title
sched/fair: Fix NEXT_BUDDY
Summary
In the Linux kernel, the following vulnerability has been resolved: sched/fair: Fix NEXT_BUDDY Adam reports that enabling NEXT_BUDDY insta triggers a WARN in pick_next_entity(). Moving clear_buddies() up before the delayed dequeue bits ensures no ->next buddy becomes delayed. Further ensure no new ->next buddy ever starts as delayed.
Severity
7 (High)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 152e11f6df293e816a6a37c69757033cdc72667d , < 5dbe6816c49197677a5ecce749bd99929da147da (git)
Affected: 152e11f6df293e816a6a37c69757033cdc72667d , < 493afbd187c4c9cc1642792c0d9ba400c3d6d90d (git)
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Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 6.12.7 , ≤ 6.12.* (semver)
Unaffected: 6.13 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
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              "value": "AV:L - The defect is in the CFS scheduler core (kernel/sched/fair.c), reached by ordinary task wakeup, sleep and load-balancer migration on the local machine. There is no remote or adjacent-network input involved, so an attacker must be able to run code on the system.\nAC:H - The entire bug is gated on the NEXT_BUDDY scheduler feature, which is `SCHED_FEAT(NEXT_BUDDY, false)` \u2014 disabled by default and settable only by root writing /sys/kernel/debug/sched/features on a CONFIG_SCHED_DEBUG=y kernel (sched_feat_write is the sole caller of sched_feat_set; there is no cmdline or sysctl path). An unprivileged attacker cannot create this precondition, and enabling NEXT_BUDDY is rare in practice, so success depends on system state outside the attacker\u0027s control.\nPR:L - Given a system with NEXT_BUDDY enabled, no special capability is needed \u2014 any unprivileged task\u0027s ordinary sleep/wake and the kernel\u0027s own load balancer (attach_task()/move_queued_task() calling wakeup_preempt() on a still-sched_delayed task) drive the code path. Only the ability to run an unprivileged process is required.\nUI:N - No victim action is needed; the reporter observed the WARN triggering instantly on ordinary system activity once the feature was enabled. Normal scheduling and CPU load balancing reach the faulty path on their own.\nS:U - The corrupted state is the kernel\u0027s own per-CPU cfs_rq bookkeeping and sched_entity flags, all within the kernel\u0027s security authority. No VM, IOMMU, or sandbox boundary is crossed.\nC:H - The scheduler is left able to run an entity that is simultaneously marked sched_delayed and blocked, which desynchronizes on_rq/nr_running/load.weight and can drive __dequeue_entity() to rb_erase an already-unlinked node, writing through a stale rb_parent pointer into memory that may have been reused. Such scheduler-structure corruption is leverageable toward reading kernel memory contents.\nI:H - A task in a non-RUNNING state is made to execute \u2014 a direct violation of a core scheduling invariant \u2014 and the resulting sched_delayed/on_rq desync leads to double account_entity_dequeue() (nr_running and load.weight underflow) and rb_erase on an unlinked rbtree node, giving a write primitive over scheduler-adjacent memory rather than a mere miscount.\nA:H - pick_next_entity() fires WARN_ONCE, which is a full kernel panic on the panic_on_warn=1 configurations used by hardened and CI deployments, and further SCHED_WARN_ONs cascade in dequeue_entity()/dequeue_entities(). Beyond the splat, the runqueue accounting underflow and rbtree corruption destabilize scheduling on the affected CPU, causing starvation, hangs, and crashes."
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    "datePublished": "2025-01-11T12:35:37.625Z",
    "dateReserved": "2025-01-11T12:32:49.536Z",
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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2025-11-25T09:01:08+00:00",
      "cve": "CVE-2024-49573",
      "id": "CVE-2024-49573",
      "initial_release_date": "2024-01-01T00:00:00+00:00",
      "product_status:known_not_affected": "276",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: sched/fair: Fix NEXT_BUDDY",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2024/cve-2024-49573.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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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.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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