From 18cdb37ebf4c986d9502405cbd16b0ac29770c25 Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Sun, 5 Oct 2014 21:28:52 -0700 Subject: net: sched: do not use tcf_proto 'tp' argument from call_rcu Using the tcf_proto pointer 'tp' from inside the classifiers callback is not valid because it may have been cleaned up by another call_rcu occuring on another CPU. 'tp' is currently being used by tcf_unbind_filter() in this patch we move instances of tcf_unbind_filter outside of the call_rcu() context. This is safe to do because any running schedulers will either read the valid class field or it will be zeroed. And all schedulers today when the class is 0 do a lookup using the same call used by the tcf_exts_bind(). So even if we have a running classifier hit the null class pointer it will do a lookup and get to the same result. This is particularly fragile at the moment because the only way to verify this is to audit the schedulers call sites. Reported-by: Cong Wang Signed-off-by: John Fastabend Acked-by: Cong Wang Signed-off-by: David S. Miller --- net/sched/cls_route.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'net/sched/cls_route.c') diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c index b665aee661f7..6f22baae0afa 100644 --- a/net/sched/cls_route.c +++ b/net/sched/cls_route.c @@ -269,9 +269,7 @@ static void route4_delete_filter(struct rcu_head *head) { struct route4_filter *f = container_of(head, struct route4_filter, rcu); - struct tcf_proto *tp = f->tp; - tcf_unbind_filter(tp, &f->res); tcf_exts_destroy(&f->exts); kfree(f); } @@ -297,6 +295,7 @@ static void route4_destroy(struct tcf_proto *tp) next = rtnl_dereference(f->next); RCU_INIT_POINTER(b->ht[h2], next); + tcf_unbind_filter(tp, &f->res); call_rcu(&f->rcu, route4_delete_filter); } } @@ -338,6 +337,7 @@ static int route4_delete(struct tcf_proto *tp, unsigned long arg) route4_reset_fastmap(head); /* Delete it */ + tcf_unbind_filter(tp, &f->res); call_rcu(&f->rcu, route4_delete_filter); /* Strip RTNL protected tree */ @@ -545,8 +545,10 @@ static int route4_change(struct net *net, struct sk_buff *in_skb, route4_reset_fastmap(head); *arg = (unsigned long)f; - if (fold) + if (fold) { + tcf_unbind_filter(tp, &fold->res); call_rcu(&fold->rcu, route4_delete_filter); + } return 0; errout: -- cgit v1.2.3-59-g8ed1b