CVE-2026-52980sched/fair: Clear rel_deadline when initializing forked entities

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.

CVSS

5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness (CWE)

Not given

Known exploited

Not in CISA's KEV catalog

EPSS (exploitation in the next 30 days)

Not loaded for this CVE

Assigned by

Linux

NVD analysis

Analyzed

Record last updated

Jun 24, 2026

First seen by InfoSec Signals

Oct 9, 2026

The CVE record on cve.org · NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.