net_cls: fix unconfigured struct tcf_proto keeps chaining and avoid kernel panic when we use cls_cgroup

This patch fixes a bug which unconfigured struct tcf_proto keeps
chaining in tc_ctl_tfilter(), and avoids kernel panic in
cls_cgroup_classify() when we use cls_cgroup.

When we execute 'tc filter add', tcf_proto is allocated, initialized
by classifier's init(), and chained.  After it's chained,
tc_ctl_tfilter() calls classifier's change().  When classifier's
change() fails, tc_ctl_tfilter() does not free and keeps tcf_proto.

In addition, cls_cgroup is initialized in change() not in init().  It
accesses unconfigured struct tcf_proto which is chained before
change(), then hits Oops.

Signed-off-by: Minoru Usui <usui@mxm.nes.nec.co.jp>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Tested-by: Minoru Usui <usui@mxm.nes.nec.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 6 deletions

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 0759f32e9dca..09cdcdfe7e91 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -135,6 +135,7 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
         unsigned long cl;
         unsigned long fh;
         int err;
+        int tp_created = 0;
 
         if (net != &init_net)
                 return -EINVAL;
@@ -266,10 +267,7 @@ replay:
                         goto errout;
                 }
 
-                spin_lock_bh(root_lock);
-                tp->next = *back;
-                *back = tp;
-                spin_unlock_bh(root_lock);
+                tp_created = 1;
 
         } else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind))
                 goto errout;
@@ -296,8 +294,11 @@ replay:
                 switch (n->nlmsg_type) {
                 case RTM_NEWTFILTER:
                         err = -EEXIST;
-                        if (n->nlmsg_flags & NLM_F_EXCL)
+                        if (n->nlmsg_flags & NLM_F_EXCL) {
+                                if (tp_created)
+                                        tcf_destroy(tp);
                                 goto errout;
+                        }
                         break;
                 case RTM_DELTFILTER:
                         err = tp->ops->delete(tp, fh);
@@ -314,8 +315,18 @@ replay:
         }
 
         err = tp->ops->change(tp, cl, t->tcm_handle, tca, &fh);
-        if (err == 0)
+        if (err == 0) {
+                if (tp_created) {
+                        spin_lock_bh(root_lock);
+                        tp->next = *back;
+                        *back = tp;
+                        spin_unlock_bh(root_lock);
+                }
                 tfilter_notify(skb, n, tp, fh, RTM_NEWTFILTER);
+        } else {
+                if (tp_created)
+                        tcf_destroy(tp);
+        }
 
 errout:
         if (cl)