this script, edited from Linux Advanced Routing and Traffic Control guide tc q a dev en0 root handle 1: htb default a tc c a dev en0 parent 1: classid 1:1 htb rate 6mbit burst 15k tc c a dev en0 parent 1:1 classid 1:a htb rate 5mbit ceil 6mbit burst 15k tc c a dev en0 parent 1:1 classid 1:b htb rate 1mbit ceil 6mbit burst 15k tc f a dev en0 parent 1:0 prio 1 $clsname $clsargs classid 1:b ping $address -c1 tc -s c s dev en0
classifies traffic to 1:b or 1:a, depending on whether the packet matches or not the pattern $clsargs of filter $clsname. However, when $clsname is 'matchall', a systematic crash can be observed in htb_classify(). HTB and classful qdiscs don't assign initial value to struct tcf_result, but then they expect it to contain valid values after filters have been run. Thus, current 'matchall' ignores the TCA_MATCHALL_CLASSID attribute, configured by user, and makes HTB (and classful qdiscs) dereference random pointers. By assigning head->res to *res in mall_classify(), before the actions are invoked, we fix this crash and enable TCA_MATCHALL_CLASSID functionality, that had no effect on 'matchall' classifier since its first introduction. BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1460213 Reported-by: Jiri Benc <jb...@redhat.com> Fixes: b87f7936a932 ("net/sched: introduce Match-all classifier") Signed-off-by: Davide Caratti <dcara...@redhat.com> --- net/sched/cls_matchall.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/sched/cls_matchall.c b/net/sched/cls_matchall.c index 21cc45caf842..eeac606c95ab 100644 --- a/net/sched/cls_matchall.c +++ b/net/sched/cls_matchall.c @@ -32,6 +32,7 @@ static int mall_classify(struct sk_buff *skb, const struct tcf_proto *tp, if (tc_skip_sw(head->flags)) return -1; + *res = head->res; return tcf_exts_exec(skb, &head->exts, res); } -- 2.13.5
