4.20-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit cd0c4e70fc0ccfa705cdf55efb27519ce9337a26 ]
Martin reported a set of filters don't work after changing from reclassify to continue. Looking into the code, it looks like skb protocol is not always fetched for each iteration of the filters. But, as demonstrated by Martin, TC actions could modify skb->protocol, for example act_vlan, this means we have to refetch skb protocol in each iteration, rather than using the one we fetch in the beginning of the loop.
This bug is _not_ introduced by commit 3b3ae880266d ("net: sched: consolidate tc_classify{,_compat}"), technically, if act_vlan is the only action that modifies skb protocol, then it is commit c7e2b9689ef8 ("sched: introduce vlan action") which introduced this bug.
Reported-by: Martin Olsson martin.olsson+netdev@sentorsecurity.com Cc: Jamal Hadi Salim jhs@mojatatu.com Cc: Jiri Pirko jiri@resnulli.us Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Acked-by: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/cls_api.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -1053,7 +1053,6 @@ static int tcf_block_cb_call(struct tcf_ int tcf_classify(struct sk_buff *skb, const struct tcf_proto *tp, struct tcf_result *res, bool compat_mode) { - __be16 protocol = tc_skb_protocol(skb); #ifdef CONFIG_NET_CLS_ACT const int max_reclassify_loop = 4; const struct tcf_proto *orig_tp = tp; @@ -1063,6 +1062,7 @@ int tcf_classify(struct sk_buff *skb, co reclassify: #endif for (; tp; tp = rcu_dereference_bh(tp->next)) { + __be16 protocol = tc_skb_protocol(skb); int err;
if (tp->protocol != protocol && @@ -1095,7 +1095,6 @@ reset: }
tp = first_tp; - protocol = tc_skb_protocol(skb); goto reclassify; #endif }