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authorJohn Fastabend <john.fastabend@gmail.com>2014-10-05 21:28:52 -0700
committerDavid S. Miller <davem@davemloft.net>2014-10-06 18:02:33 -0400
commit18cdb37ebf4c986d9502405cbd16b0ac29770c25 (patch)
tree2bf659bf5d527447c11845ca06d15d1b69b9ab31 /net/sched/cls_basic.c
parent13990f8156862fe945a1a226850a6550c8988a33 (diff)
downloadlinux-18cdb37ebf4c986d9502405cbd16b0ac29770c25.tar.bz2
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 <xiyou.wangconf@gmail.com> Signed-off-by: John Fastabend <john.r.fastabend@intel.com> Acked-by: Cong Wang <cwang@twopensource.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/cls_basic.c')
-rw-r--r--net/sched/cls_basic.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/net/sched/cls_basic.c b/net/sched/cls_basic.c
index 90647a8af8ca..cd61280941e5 100644
--- a/net/sched/cls_basic.c
+++ b/net/sched/cls_basic.c
@@ -91,9 +91,7 @@ static int basic_init(struct tcf_proto *tp)
static void basic_delete_filter(struct rcu_head *head)
{
struct basic_filter *f = container_of(head, struct basic_filter, rcu);
- struct tcf_proto *tp = f->tp;
- tcf_unbind_filter(tp, &f->res);
tcf_exts_destroy(&f->exts);
tcf_em_tree_destroy(&f->ematches);
kfree(f);
@@ -106,6 +104,7 @@ static void basic_destroy(struct tcf_proto *tp)
list_for_each_entry_safe(f, n, &head->flist, link) {
list_del_rcu(&f->link);
+ tcf_unbind_filter(tp, &f->res);
call_rcu(&f->rcu, basic_delete_filter);
}
RCU_INIT_POINTER(tp->root, NULL);
@@ -120,6 +119,7 @@ static int basic_delete(struct tcf_proto *tp, unsigned long arg)
list_for_each_entry(t, &head->flist, link)
if (t == f) {
list_del_rcu(&t->link);
+ tcf_unbind_filter(tp, &t->res);
call_rcu(&t->rcu, basic_delete_filter);
return 0;
}
@@ -222,6 +222,7 @@ static int basic_change(struct net *net, struct sk_buff *in_skb,
if (fold) {
list_replace_rcu(&fold->link, &fnew->link);
+ tcf_unbind_filter(tp, &fold->res);
call_rcu(&fold->rcu, basic_delete_filter);
} else {
list_add_rcu(&fnew->link, &head->flist);