Messages in this thread | | | From | Jamal Hadi Salim <> | Date | Fri, 15 Sep 2023 18:55:05 -0400 | Subject | Re: [PATCH] net: sched: drr: dont intepret cls results when asked to drop |
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On Fri, Sep 15, 2023 at 11:06 AM Eric Dumazet <edumazet@google.com> wrote: > > On Fri, Sep 15, 2023 at 5:03 PM Pedro Tammela <pctammela@mojatatu.com> wrote: > > > > On 15/09/2023 09:55, Eric Dumazet wrote: > > > On Fri, Sep 15, 2023 at 12:42 PM Ma Ke <make_ruc2021@163.com> wrote: > > >> > > >> If asked to drop a packet via TC_ACT_SHOT it is unsafe to > > >> assume res.class contains a valid pointer. > > >> > > >> Signed-off-by: Ma Ke <make_ruc2021@163.com> > > >> --- > > >> net/sched/sch_drr.c | 2 ++ > > >> 1 file changed, 2 insertions(+) > > >> > > >> diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c > > >> index 19901e77cd3b..2b854cb6edf9 100644 > > >> --- a/net/sched/sch_drr.c > > >> +++ b/net/sched/sch_drr.c > > >> @@ -309,6 +309,8 @@ static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch, > > >> *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; > > >> fl = rcu_dereference_bh(q->filter_list); > > >> result = tcf_classify(skb, NULL, fl, &res, false); > > >> + if (result == TC_ACT_SHOT) > > >> + return NULL; > > >> if (result >= 0) { > > >> #ifdef CONFIG_NET_CLS_ACT > > >> switch (result) { > > >> -- > > >> 2.37.2 > > >> > > > > > > I do not see a bug, TC_ACT_SHOT is handled in the switch (result) just fine > > > at line 320 ? > > > > Following the code path (with CONFIG_NET_CLS_ACT=n in mind), it looks > > like there are a couple of places which return TC_ACT_SHOT before > > calling any classifiers, which then would cause some qdiscs to look into > > a uninitialized 'struct tcf_result res'. > > I could be misreading it... But if it's the problem the author is trying > > to fix, the obvious way to do it would be: > > struct tcf_result res = {}; > > CONFIG_NET_CLS_ACT=n, how come TC_ACT_SHOT could be used ? > > Can we get rid of CONFIG_NET_CLS_ACT, this seems obfuscation to me at > this point.
The problem is the verdict vs return code are intermixed - not saying this was fixing anything useful. We discussed this in the past after/during commit caa4b35b4317d5147b3ab0fbdc9c075c7d2e9c12 Victor worked on a patch to resolve that. Victor, maybe revive that patch and post as RFC?
cheers, jamal
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