---
id: CVE-2026-52980
title: |-
  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…
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…
severity: none
published: '2026-06-24'
updated: '2026-07-10'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52980'
references:
  - url: 'https://git.kernel.org/stable/c/3da56dc063cd77b9c0b40add930767fab4e389f3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8f4a16200785f49cf02c5b71bdfe7a9dab63f23a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c71bf35caba12bfd9bc23e32b0bcd9e02d1cf1ac'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f3c16e1f4a314a20717ab90a41885f8111a242ab'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00162
epssPercentile: 0.04585
ingestedAt: '2026-07-11T13:13:25.428Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.