sched/fair: Fix zero_vruntime tracking fix
Summary
| CVE | CVE-2026-43323 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-08 14:16:40 UTC |
| Updated | 2026-05-12 14:10:27 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: sched/fair: Fix zero_vruntime tracking fix John reported that stress-ng-yield could make his machine unhappy and managed to bisect it to commit b3d99f43c72b ("sched/fair: Fix zero_vruntime tracking"). The combination of yield and that commit was specific enough to hypothesize the following scenario: Suppose we have 2 runnable tasks, both doing yield. Then one will be eligible and one will not be, because the average position must be in between these two entities. Therefore, the runnable task will be eligible, and be promoted a full slice (all the tasks do is yield after all). This causes it to jump over the other task and now the other task is eligible and current is no longer. So we schedule. Since we are runnable, there is no {de,en}queue. All we have is the __{en,de}queue_entity() from {put_prev,set_next}_task(). But per the fingered commit, those two no longer move zero_vruntime. All that moves zero_vruntime are tick and full {de,en}queue. This means, that if the two tasks playing leapfrog can reach the critical speed to reach the overflow point inside one tick's worth of time, we're up a creek. Additionally, when multiple cgroups are involved, there is no guarantee the tick will in fact hit every cgroup in a timely manner. Statistically speaking it will, but that same statistics does not rule out the possibility of one cgroup not getting a tick for a significant amount of time -- however unlikely. Therefore, just like with the yield() case, force an update at the end of every slice. This ensures the update is never more than a single slice behind and the whole thing is within 2 lag bounds as per the comment on entity_key(). |
Risk And Classification
EPSS: 0.000180000 probability, percentile 0.047280000 (date 2026-05-11)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected d2fc2dcfce47a56ffd414783003cc966c742c8a9 c089147074ed96ff4330739a0559394c19a3dfc8 git | Not specified |
| CNA | Linux | Linux | affected 99673934a89febe664e704550216638dcb2336a8 87573883c30f1a8555ff720836bb6ea231058539 git | Not specified |
| CNA | Linux | Linux | affected 978d4fe59665c13db692ba96839f9c52d69f13f3 fb61ffb3fb30a161eb5404c27fc7635e275beafd git | Not specified |
| CNA | Linux | Linux | affected b3d99f43c72b56cf7a104a364e7fb34b0702828b 1319ea57529e131822bab56bf417c8edc2db9ae8 git | Not specified |
| CNA | Linux | Linux | affected 6.12.78 6.12.81 semver | Not specified |
| CNA | Linux | Linux | affected 6.18.17 6.18.22 semver | Not specified |
| CNA | Linux | Linux | affected 6.19.7 6.19.12 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/c089147074ed96ff4330739a0559394c19a3dfc8 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/1319ea57529e131822bab56bf417c8edc2db9ae8 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/fb61ffb3fb30a161eb5404c27fc7635e275beafd | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/87573883c30f1a8555ff720836bb6ea231058539 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.