net/sched: sch_hfsc: Don't make class passive twice
Summary
| CVE | CVE-2026-74284 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-15 06:22:27 UTC |
| Updated | 2026-08-17 06:19:22 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_hfsc: Don't make class passive twice update_vf() is called from two places for the same class during a single dequeue when the class's child qdisc (e.g. codel/fq_codel) drops its last packets while dequeuing: 1. The child calls qdisc_tree_reduce_backlog(), which, now that the child is empty, invokes hfsc_qlen_notify() -> update_vf(cl, 0, 0) and turns the class passive (cl_nactive is decremented up the hierarchy). 2. hfsc_dequeue() then calls update_vf(cl, qdisc_pkt_len(skb), cur_time) to charge the dequeued bytes. On the second call the class is already passive, but its child qdisc is still empty, so update_vf() arms go_passive again: if (cl->qdisc->q.qlen == 0 && cl->cl_flags & HFSC_FSC) go_passive = 1; The leaf is then skipped by the cl_nactive == 0 check inside the loop, which does not clear go_passive, so the stale go_passive propagates to the parent and decrements its cl_nactive a second time. A parent that still has other active children is driven to cl_nactive == 0 and removed from the vttree, even though those siblings are still backlogged. They are never dequeued again and the qdisc stalls. Fix this by only arming go_passive when the class is actually active, so an already-passive class no longer triggers a second passive transition. The byte accounting (cl->cl_total += len) still runs for every ancestor, so dequeued bytes continue to be counted exactly once. |
Risk And Classification
EPSS: 0.002100000 probability, percentile 0.115390000 (date 2026-08-17)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7 a425c82ff06cda5165e0de3de8c2a445ec1f863e git | Not specified |
| CNA | Linux | Linux | affected a5efc95a33bd4fcb879250852828cc58c7862970 fc973ecd1a079b9a87c360478542f3a56dea085b git | Not specified |
| CNA | Linux | Linux | affected 0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87 15720cd8fa3fc625146128f89a8e11b0449a20a7 git | Not specified |
| CNA | Linux | Linux | affected 9030a91235ae4845ec71902c3e0cecfc9ed1f2df b2a017bfcf565721918ec7355a373911d2f2a227 git | Not specified |
| CNA | Linux | Linux | affected d06476714d2819b550e0cc39222347e2c8941c9d 9221a594c72a1446137926d4c2aa04e345f798dc git | Not specified |
| CNA | Linux | Linux | affected 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb 66dbb13eeb2fc339f8f548a9076be4c1a94857b0 git | Not specified |
| CNA | Linux | Linux | affected 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb 3a49bbae676fef1ffe548971e6229ae2adeb9d10 git | Not specified |
| CNA | Linux | Linux | affected 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb 90b662ea25f5e83bb3b8ccec5b93ced810b92fb8 git | Not specified |
| CNA | Linux | Linux | affected 9a5fd5c2f4d4afdd5e405083ee53e0789ce76956 git | Not specified |
| CNA | Linux | Linux | affected c1175c4ad01dbc9c979d099861fa90a754f72059 git | Not specified |
| CNA | Linux | Linux | affected 5.10.241 5.10.261 semver | Not specified |
| CNA | Linux | Linux | affected 5.15.190 5.15.212 semver | Not specified |
| CNA | Linux | Linux | affected 6.1.138 6.1.178 semver | Not specified |
| CNA | Linux | Linux | affected 6.6.90 6.6.145 semver | Not specified |
| CNA | Linux | Linux | affected 6.12.28 6.12.97 semver | Not specified |
| CNA | Linux | Linux | affected 5.4.297 5.5 semver | Not specified |
| CNA | Linux | Linux | affected 6.14.6 6.15 semver | Not specified |
| CNA | Linux | Linux | affected 6.15 | Not specified |
| CNA | Linux | Linux | unaffected 6.15 semver | Not specified |
| CNA | Linux | Linux | unaffected 5.10.261 5.10.* semver | Not specified |
| CNA | Linux | Linux | unaffected 5.15.212 5.15.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.1.178 6.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.145 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.97 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.40 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1.5 7.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/fc973ecd1a079b9a87c360478542f3a56dea085b | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/b2a017bfcf565721918ec7355a373911d2f2a227 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/90b662ea25f5e83bb3b8ccec5b93ced810b92fb8 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/15720cd8fa3fc625146128f89a8e11b0449a20a7 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/a425c82ff06cda5165e0de3de8c2a445ec1f863e | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/9221a594c72a1446137926d4c2aa04e345f798dc | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/66dbb13eeb2fc339f8f548a9076be4c1a94857b0 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/3a49bbae676fef1ffe548971e6229ae2adeb9d10 | 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.