Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: fq_codel: clamp default quantum and mtu fq_codel_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) without clamping. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000, which overflows the signed flow->deficit to INT_MIN in fq_codel_dequeue(), causing an infinite loop and soft lockup. Emulate fq_codel_change() and constrain to [256, FQ_CODEL_QUANTUM_MAX]. The same unclamped psched_mtu() is assigned to q->cparams.mtu a bit below, and fq_codel_change() never updates it. codel_should_drop() tests "*backlog <= params->mtu"; with mtu == 0x80000000 (~2 GiB) and the default 32 MiB memory_limit, the test is always true, so CoDel is silently and completely disabled (no drops, no ECN). Declare a single clamped mtu and assign both q->quantum and q->cparams.mtu from it, which also removes the double psched_mtu() call. Conditions to recreate the bug: a device whose MTU (plus hard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy device with max_mtu == 0 accepting MTU 2147483634). Requires CAP_NET_ADMIN in a user namespace.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
4b549a2ef4bef9965d97cbd992ba67930cd3e0fe to < d315ee8a07fd1810880227319cf60e6cd925ef22affected4b549a2ef4bef9965d97cbd992ba67930cd3e0fe to < a9a5b2943a00df2ab81a2209f31dd9e87016f120affected4b549a2ef4bef9965d97cbd992ba67930cd3e0fe to < 3782067ec0d485628b6f1f9ede3eeeb4f611fcf2affected4b549a2ef4bef9965d97cbd992ba67930cd3e0fe to < 397e2b1f71d9f15b8b4e47d24eb620e4dff8878daffected4b549a2ef4bef9965d97cbd992ba67930cd3e0fe to < 324f86806673ae4a55f66d28db84577f46f615e1affected4b549a2ef4bef9965d97cbd992ba67930cd3e0fe to < dfb4b61db886917244284b18b44b23d2254b82c2affected4b549a2ef4bef9965d97cbd992ba67930cd3e0fe to < 9f499e5827fdb6d7fdb46a7ce731852f6b1a1bb9affected4b549a2ef4bef9965d97cbd992ba67930cd3e0fe to < d9ebd8f9aa8b2773235889cb903fafd61f2d8585affected
Linux Linux
Default version status: affected
3.5affected0 to < 3.5unaffected5.10.270 to ≤ 5.10.*unaffected5.15.221 to ≤ 5.15.*unaffected6.1.188 to ≤ 6.1.*unaffected6.6.157 to ≤ 6.6.*unaffected6.12.110 to ≤ 6.12.*unaffected6.18.52 to ≤ 6.18.*unaffected7.2.6 to ≤ 7.2.*unaffected7.3 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/d315ee8a07fd1810880227319cf60e6cd925ef22 ↗
- https://git.kernel.org/stable/c/a9a5b2943a00df2ab81a2209f31dd9e87016f120 ↗
- https://git.kernel.org/stable/c/3782067ec0d485628b6f1f9ede3eeeb4f611fcf2 ↗
- https://git.kernel.org/stable/c/397e2b1f71d9f15b8b4e47d24eb620e4dff8878d ↗
- https://git.kernel.org/stable/c/324f86806673ae4a55f66d28db84577f46f615e1 ↗
- https://git.kernel.org/stable/c/dfb4b61db886917244284b18b44b23d2254b82c2 ↗
- https://git.kernel.org/stable/c/9f499e5827fdb6d7fdb46a7ce731852f6b1a1bb9 ↗
- https://git.kernel.org/stable/c/d9ebd8f9aa8b2773235889cb903fafd61f2d8585 ↗