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_fw.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net/sched/cls_fw.c') diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c index da805aeeb65c..dbfdfd1f1a9f 100644 --- a/net/sched/cls_fw.c +++ b/net/sched/cls_fw.c @@ -123,9 +123,7 @@ static int fw_init(struct tcf_proto *tp) static void fw_delete_filter(struct rcu_head *head) { struct fw_filter *f = container_of(head, struct fw_filter, rcu); - struct tcf_proto *tp = f->tp; - tcf_unbind_filter(tp, &f->res); tcf_exts_destroy(&f->exts); kfree(f); } @@ -143,6 +141,7 @@ static void fw_destroy(struct tcf_proto *tp) while ((f = rtnl_dereference(head->ht[h])) != NULL) { RCU_INIT_POINTER(head->ht[h], rtnl_dereference(f->next)); + tcf_unbind_filter(tp, &f->res); call_rcu(&f->rcu, fw_delete_filter); } } @@ -166,6 +165,7 @@ static int fw_delete(struct tcf_proto *tp, unsigned long arg) fp = &pfp->next, pfp = rtnl_dereference(*fp)) { if (pfp == f) { RCU_INIT_POINTER(*fp, rtnl_dereference(f->next)); + tcf_unbind_filter(tp, &f->res); call_rcu(&f->rcu, fw_delete_filter); return 0; } @@ -280,6 +280,7 @@ static int fw_change(struct net *net, struct sk_buff *in_skb, RCU_INIT_POINTER(fnew->next, rtnl_dereference(pfp->next)); rcu_assign_pointer(*fp, fnew); + tcf_unbind_filter(tp, &f->res); call_rcu(&f->rcu, fw_delete_filter); *arg = (unsigned long)fnew; -- cgit v1.2.3