On Wed, Jun 11, 2025 at 08:35:01AM +0000, Eric Dumazet wrote:
Gerrard Tai reported that SFQ perturb_period has no range check yet, and this can be used to trigger a race condition fixed in a separate patch.
We want to make sure ctl->perturb_period * HZ will not overflow and is positive.
Tested:
tc qd add dev lo root sfq perturb -10 # negative value : error Error: sch_sfq: invalid perturb period.
tc qd add dev lo root sfq perturb 1000000000 # too big : error Error: sch_sfq: invalid perturb period.
tc qd add dev lo root sfq perturb 2000000 # acceptable value tc -s -d qd sh dev lo qdisc sfq 8005: root refcnt 2 limit 127p quantum 64Kb depth 127 flows 128 divisor 1024 perturb 2000000sec Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0
Please kindly provide a selftest (as a separate patch) since it looks fairly easy to reproduce. With AI copilot today, this becomes much easier, so hopefully it won't bring you much burden. :)
Thanks.