net: sched: prevent insertion of new classifiers during chain flush

Extend tcf_chain with 'flushing' flag. Use the flag to prevent insertion of
new classifier instances when chain flushing is in progress in order to
prevent resource leak when tcf_proto is created by unlocked users
concurrently.

Return EAGAIN error from tcf_chain_tp_insert_unique() to restart
tc_new_tfilter() and lookup the chain/proto again.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 083e566fc38089e8a6a1fe1b28c632abb2bff643..e8cf36ed3e8769d9b58b113a36bcbc0707fa0e84 100644 (file)
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -356,6 +356,7 @@ struct tcf_chain {
        unsigned int refcnt;
        unsigned int action_refcnt;
        bool explicitly_created;
+       bool flushing;
        const struct tcf_proto_ops *tmplt_ops;
        void *tmplt_priv;
 };

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index c6452e3bfc6a99ab62a61b3295693b270cf52962..3038a82f6591f10446a9accf51fa3535f678fef9 100644 (file)
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -477,9 +477,12 @@ static void __tcf_chain_put(struct tcf_chain *chain, bool by_act,
        mutex_unlock(&block->lock);
 
        /* The last dropped non-action reference will trigger notification. */
-       if (is_last && !by_act)
+       if (is_last && !by_act) {
                tc_chain_notify_delete(tmplt_ops, tmplt_priv, chain_index,
                                       block, NULL, 0, 0, false);
+               /* Last reference to chain, no need to lock. */
+               chain->flushing = false;
+       }
 
        if (refcnt == 0) {
                tc_chain_tmplt_del(tmplt_ops, tmplt_priv);
@@ -511,6 +514,7 @@ static void tcf_chain_flush(struct tcf_chain *chain)
        tp = tcf_chain_dereference(chain->filter_chain, chain);
        RCU_INIT_POINTER(chain->filter_chain, NULL);
        tcf_chain0_head_change(chain, NULL);
+       chain->flushing = true;
        mutex_unlock(&chain->filter_chain_lock);
 
        while (tp) {
@@ -1610,15 +1614,20 @@ static struct tcf_proto *tcf_chain_tp_prev(struct tcf_chain *chain,
        return tcf_chain_dereference(*chain_info->pprev, chain);
 }
 
-static void tcf_chain_tp_insert(struct tcf_chain *chain,
-                               struct tcf_chain_info *chain_info,
-                               struct tcf_proto *tp)
+static int tcf_chain_tp_insert(struct tcf_chain *chain,
+                              struct tcf_chain_info *chain_info,
+                              struct tcf_proto *tp)
 {
+       if (chain->flushing)
+               return -EAGAIN;
+
        if (*chain_info->pprev == chain->filter_chain)
                tcf_chain0_head_change(chain, tp);
        tcf_proto_get(tp);
        RCU_INIT_POINTER(tp->next, tcf_chain_tp_prev(chain, chain_info));
        rcu_assign_pointer(*chain_info->pprev, tp);
+
+       return 0;
 }
 
 static void tcf_chain_tp_remove(struct tcf_chain *chain,
@@ -1649,18 +1658,22 @@ static struct tcf_proto *tcf_chain_tp_insert_unique(struct tcf_chain *chain,
 {
        struct tcf_chain_info chain_info;
        struct tcf_proto *tp;
+       int err = 0;
 
        mutex_lock(&chain->filter_chain_lock);
 
        tp = tcf_chain_tp_find(chain, &chain_info,
                               protocol, prio, false);
        if (!tp)
-               tcf_chain_tp_insert(chain, &chain_info, tp_new);
+               err = tcf_chain_tp_insert(chain, &chain_info, tp_new);
        mutex_unlock(&chain->filter_chain_lock);
 
        if (tp) {
                tcf_proto_destroy(tp_new, NULL);
                tp_new = tp;
+       } else if (err) {
+               tcf_proto_destroy(tp_new, NULL);
+               tp_new = ERR_PTR(err);
        }
 
        return tp_new;
@@ -1943,6 +1956,11 @@ replay:
        if (tp == NULL) {
                struct tcf_proto *tp_new = NULL;
 
+               if (chain->flushing) {
+                       err = -EAGAIN;
+                       goto errout_locked;
+               }
+
                /* Proto-tcf does not exist, create new one */
 
                if (tca[TCA_KIND] == NULL || !protocol) {
@@ -1966,11 +1984,15 @@ replay:
                                          protocol, prio, chain, extack);
                if (IS_ERR(tp_new)) {
                        err = PTR_ERR(tp_new);
-                       goto errout;
+                       goto errout_tp;
                }
 
                tp_created = 1;
                tp = tcf_chain_tp_insert_unique(chain, tp_new, protocol, prio);
+               if (IS_ERR(tp)) {
+                       err = PTR_ERR(tp);
+                       goto errout_tp;
+               }
        } else {
                mutex_unlock(&chain->filter_chain_lock);
        }
@@ -2011,6 +2033,7 @@ replay:
 errout:
        if (err && tp_created)
                tcf_chain_tp_delete_empty(chain, tp, NULL);
+errout_tp:
        if (chain) {
                if (tp && !IS_ERR(tp))
                        tcf_proto_put(tp, NULL);