Description (CNA)
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.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 72c61ffbeeb8c50f6d4d70c65d3283aa1bac57a7 before a425c82ff06cda5165e0de3de8c2a445ec1f863e; affected a5efc95a33bd4fcb879250852828cc58c7862970 before fc973ecd1a079b9a87c360478542f3a56dea085b; affected 0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87 before 15720cd8fa3fc625146128f89a8e11b0449a20a7; affected 9030a91235ae4845ec71902c3e0cecfc9ed1f2df before b2a017bfcf565721918ec7355a373911d2f2a227; affected d06476714d2819b550e0cc39222347e2c8941c9d before 9221a594c72a1446137926d4c2aa04e345f798dc; affected 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb before 66dbb13eeb2fc339f8f548a9076be4c1a94857b0; affected 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb before 3a49bbae676fef1ffe548971e6229ae2adeb9d10; affected 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb before 90b662ea25f5e83bb3b8ccec5b93ced810b92fb8; affected 9a5fd5c2f4d4afdd5e405083ee53e0789ce76956; affected c1175c4ad01dbc9c979d099861fa90a754f72059; affected 5.10.241 before 5.10.261; affected 5.15.190 before 5.15.212; affected 6.1.138 before 6.1.178; affected 6.6.90 before 6.6.145; affected 6.12.28 before 6.12.97; affected 5.4.297 before 5.5; affected 6.14.6 before 6.15 |
| Linux / Linux | affected 6.15; unaffected 0 before 6.15; unaffected 5.10.261 through 5.10.*; unaffected 5.15.212 through 5.15.*; unaffected 6.1.178 through 6.1.*; unaffected 6.6.145 through 6.6.*; unaffected 6.12.97 through 6.12.*; unaffected 6.18.40 through 6.18.*; unaffected 7.1.5 through 7.1.*; unaffected 7.2 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/a425c82ff06cda5165e0de3de8c2a445ec1f863e
- https://git.kernel.org/stable/c/fc973ecd1a079b9a87c360478542f3a56dea085b
- https://git.kernel.org/stable/c/15720cd8fa3fc625146128f89a8e11b0449a20a7
- https://git.kernel.org/stable/c/b2a017bfcf565721918ec7355a373911d2f2a227
- https://git.kernel.org/stable/c/9221a594c72a1446137926d4c2aa04e345f798dc
- https://git.kernel.org/stable/c/66dbb13eeb2fc339f8f548a9076be4c1a94857b0
- https://git.kernel.org/stable/c/3a49bbae676fef1ffe548971e6229ae2adeb9d10
- https://git.kernel.org/stable/c/90b662ea25f5e83bb3b8ccec5b93ced810b92fb8