PT-2026-54796 · Linux · Linux
Published
2026-07-01
·
Updated
2026-07-01
·
CVE-2026-53328
None
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In the Linux kernel, the following vulnerability has been resolved:
sched ext: Don't warn on NULL cgrp moving from in scx cgroup move task()
A WARN fires when systemd's user manager writes "+cpu +memory +pids" to
its own subtree control while a sched ext scheduler is loaded:
WARNING: at kernel/sched/ext.c:3227 scx cgroup move task+0xa8/0xb0
scx cgroup move task+0xa8/0xb0
sched move task+0x134/0x290
cpu cgroup attach+0x39/0x70
cgroup migrate execute+0x37d/0x450
cgroup update dfl csses+0x1e3/0x270
cgroup subtree control write+0x3e7/0x440
scx cgroup can attach() arms cgrp moving from only when a task's cpu
cgroup changes. It can still be NULL when scx cgroup move task() runs,
through this sequence:
Step Result
- cpu enabled on cgroup G cpu css = A
- cpu toggled off then on for G A killed, B created (same cgroup)
- an exiting task keeps A alive migration skips it, A now stale
- +memory migrates G stale A vs current B pulls cpu in
- cpu attach runs for all tasks hits a live, cpu-unchanged task
- scx cgroup move task() on it cgrp moving from NULL -> WARN
The mismatch is that scx cgroup can attach() keys on cgroup identity
while migration drives the move on css identity, so a NULL cgrp moving from
here is a legitimate css-only migration, not a missing prep.
The call is already gated on cgrp moving from, so just drop the warning.
ops.cgroup prep move() and ops.cgroup move() stay paired.
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Related Identifiers
Affected Products
Linux