CVE-2026-52980 (GCVE-0-2026-52980)

Vulnerability from cvelistv5 – Published: 2026-06-24 16:28 – Updated: 2026-06-24 16:28
VLAI
Title
sched/fair: Clear rel_deadline when initializing forked entities
Summary
In the Linux kernel, the following vulnerability has been resolved: sched/fair: Clear rel_deadline when initializing forked entities A yield-triggered crash can happen when a newly forked sched_entity enters the fair class with se->rel_deadline unexpectedly set. The failing sequence is: 1. A task is forked while se->rel_deadline is still set. 2. __sched_fork() initializes vruntime, vlag and other sched_entity state, but does not clear rel_deadline. 3. On the first enqueue, enqueue_entity() calls place_entity(). 4. Because se->rel_deadline is set, place_entity() treats se->deadline as a relative deadline and converts it to an absolute deadline by adding the current vruntime. 5. However, the forked entity's deadline is not a valid inherited relative deadline for this new scheduling instance, so the conversion produces an abnormally large deadline. 6. If the task later calls sched_yield(), yield_task_fair() advances se->vruntime to se->deadline. 7. The inflated vruntime is then used by the following enqueue path, where the vruntime-derived key can overflow when multiplied by the entity weight. 8. This corrupts cfs_rq->sum_w_vruntime, breaks EEVDF eligibility calculation, and can eventually make all entities appear ineligible. pick_next_entity() may then return NULL unexpectedly, leading to a later NULL dereference. A captured trace shows the effect clearly. Before yield, the entity's vruntime was around: 9834017729983308 After yield_task_fair() executed: se->vruntime = se->deadline the vruntime jumped to: 19668035460670230 and the deadline was later advanced further to: 19668035463470230 This shows that the deadline had already become abnormally large before yield_task_fair() copied it into vruntime. rel_deadline is only meaningful when se->deadline really carries a relative deadline that still needs to be placed against vruntime. A freshly forked sched_entity should not inherit or retain this state. Clear se->rel_deadline in __sched_fork(), together with the other sched_entity runtime state, so that the first enqueue does not interpret the new entity's deadline as a stale relative deadline.
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 82e9d0456e06cebe2c89f3c73cdbc9e3805e9437 , < c71bf35caba12bfd9bc23e32b0bcd9e02d1cf1ac (git)
Affected: 82e9d0456e06cebe2c89f3c73cdbc9e3805e9437 , < f3c16e1f4a314a20717ab90a41885f8111a242ab (git)
Affected: 82e9d0456e06cebe2c89f3c73cdbc9e3805e9437 , < 8f4a16200785f49cf02c5b71bdfe7a9dab63f23a (git)
Affected: 82e9d0456e06cebe2c89f3c73cdbc9e3805e9437 , < 3da56dc063cd77b9c0b40add930767fab4e389f3 (git)
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Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 6.12.91 , ≤ 6.12.* (semver)
Unaffected: 6.18.33 , ≤ 6.18.* (semver)
Unaffected: 7.0.10 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/fair: Clear rel_deadline when initializing forked entities\n\nA yield-triggered crash can happen when a newly forked sched_entity\nenters the fair class with se-\u003erel_deadline unexpectedly set.\n\nThe failing sequence is:\n\n  1. A task is forked while se-\u003erel_deadline is still set.\n  2. __sched_fork() initializes vruntime, vlag and other sched_entity\n     state, but does not clear rel_deadline.\n  3. On the first enqueue, enqueue_entity() calls place_entity().\n  4. Because se-\u003erel_deadline is set, place_entity() treats se-\u003edeadline\n     as a relative deadline and converts it to an absolute deadline by\n     adding the current vruntime.\n  5. However, the forked entity\u0027s deadline is not a valid inherited\n     relative deadline for this new scheduling instance, so the conversion\n     produces an abnormally large deadline.\n  6. If the task later calls sched_yield(), yield_task_fair() advances\n     se-\u003evruntime to se-\u003edeadline.\n  7. The inflated vruntime is then used by the following enqueue path,\n     where the vruntime-derived key can overflow when multiplied by the\n     entity weight.\n  8. This corrupts cfs_rq-\u003esum_w_vruntime, breaks EEVDF eligibility\n     calculation, and can eventually make all entities appear ineligible.\n     pick_next_entity() may then return NULL unexpectedly, leading to a\n     later NULL dereference.\n\nA captured trace shows the effect clearly. Before yield, the entity\u0027s\nvruntime was around:\n\n  9834017729983308\n\nAfter yield_task_fair() executed:\n\n  se-\u003evruntime = se-\u003edeadline\n\nthe vruntime jumped to:\n\n  19668035460670230\n\nand the deadline was later advanced further to:\n\n  19668035463470230\n\nThis shows that the deadline had already become abnormally large before\nyield_task_fair() copied it into vruntime.\n\nrel_deadline is only meaningful when se-\u003edeadline really carries a\nrelative deadline that still needs to be placed against vruntime. A\nfreshly forked sched_entity should not inherit or retain this state.\nClear se-\u003erel_deadline in __sched_fork(), together with the other\nsched_entity runtime state, so that the first enqueue does not interpret\nthe new entity\u0027s deadline as a stale relative deadline."
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Because se-\u003erel_deadline is set, place_entity() treats se-\u003edeadline\\n     as a relative deadline and converts it to an absolute deadline by\\n     adding the current vruntime.\\n  5. However, the forked entity\u0027s deadline is not a valid inherited\\n     relative deadline for this new scheduling instance, so the conversion\\n     produces an abnormally large deadline.\\n  6. If the task later calls sched_yield(), yield_task_fair() advances\\n     se-\u003evruntime to se-\u003edeadline.\\n  7. The inflated vruntime is then used by the following enqueue path,\\n     where the vruntime-derived key can overflow when multiplied by the\\n     entity weight.\\n  8. This corrupts cfs_rq-\u003esum_w_vruntime, breaks EEVDF eligibility\\n     calculation, and can eventually make all entities appear ineligible.\\n     pick_next_entity() may then return NULL unexpectedly, leading to a\\n     later NULL dereference.\\n\\nA captured trace shows the effect clearly. 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    "redhat_vex": {
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      "current_release_date": "2026-07-14T18:05:02+00:00",
      "cve": "CVE-2026-52980",
      "id": "CVE-2026-52980",
      "initial_release_date": "2026-06-24T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: sched/fair: Clear rel_deadline when initializing forked entities",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52980.json",
      "version": "3"
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      "current_release_date": "2026-06-27T01:55:04Z",
      "cve": "CVE-2026-52980",
      "id": "CVE-2026-52980",
      "initial_release_date": "2026-06-27T01:55:04Z",
      "product_status:known_not_affected": "291",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-52980",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-52980.json",
      "version": "2"
    }
  }
}



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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.

Sightings

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Nomenclature

  • 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.
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  • 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.


Detection rules are retrieved from Rulezet.