net: sched: protect block->chain0 with block->lock

In order to remove dependency on rtnl lock, use block->lock to protect
chain0 struct from concurrent modification. Rearrange code in chain0
callback add and del functions to only access chain0 when block->lock is
held.

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/net/sched/cls_api.c b/net/sched/cls_api.c
index b5db0f7..869ae44 100644 (file)
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -244,8 +244,11 @@ static void tcf_chain0_head_change(struct tcf_chain *chain,
 
        if (chain->index)
                return;
+
+       mutex_lock(&block->lock);
        list_for_each_entry(item, &block->chain0.filter_chain_list, list)
                tcf_chain_head_change_item(item, tp_head);
+       mutex_unlock(&block->lock);
 }
 
 /* Returns true if block can be safely freed. */
@@ -756,8 +759,8 @@ tcf_chain0_head_change_cb_add(struct tcf_block *block,
                              struct tcf_block_ext_info *ei,
                              struct netlink_ext_ack *extack)
 {
-       struct tcf_chain *chain0 = block->chain0.chain;
        struct tcf_filter_chain_list_item *item;
+       struct tcf_chain *chain0;
 
        item = kmalloc(sizeof(*item), GFP_KERNEL);
        if (!item) {
@@ -766,9 +769,14 @@ tcf_chain0_head_change_cb_add(struct tcf_block *block,
        }
        item->chain_head_change = ei->chain_head_change;
        item->chain_head_change_priv = ei->chain_head_change_priv;
+
+       mutex_lock(&block->lock);
+       chain0 = block->chain0.chain;
        if (chain0 && chain0->filter_chain)
                tcf_chain_head_change_item(item, chain0->filter_chain);
        list_add(&item->list, &block->chain0.filter_chain_list);
+       mutex_unlock(&block->lock);
+
        return 0;
 }
 
@@ -776,20 +784,23 @@ static void
 tcf_chain0_head_change_cb_del(struct tcf_block *block,
                              struct tcf_block_ext_info *ei)
 {
-       struct tcf_chain *chain0 = block->chain0.chain;
        struct tcf_filter_chain_list_item *item;
 
+       mutex_lock(&block->lock);
        list_for_each_entry(item, &block->chain0.filter_chain_list, list) {
                if ((!ei->chain_head_change && !ei->chain_head_change_priv) ||
                    (item->chain_head_change == ei->chain_head_change &&
                     item->chain_head_change_priv == ei->chain_head_change_priv)) {
-                       if (chain0)
+                       if (block->chain0.chain)
                                tcf_chain_head_change_item(item, NULL);
                        list_del(&item->list);
+                       mutex_unlock(&block->lock);
+
                        kfree(item);
                        return;
                }
        }
+       mutex_unlock(&block->lock);
        WARN_ON(1);
 }