From b064d0d88ae5280c7e878f79d0c9a8e2876a4d14 Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Mon, 18 Jan 2016 18:03:48 +0100 Subject: [PATCH] ovs: limit ovs recursions in ovs_execute_actions to not corrupt stack It was seen that defective configurations of openvswitch could overwrite the STACK_END_MAGIC and cause a hard crash of the kernel because of too many recursions within ovs. This problem arises due to the high stack usage of openvswitch. The rest of the kernel is fine with the current limit of 10 (RECURSION_LIMIT). We use the already existing recursion counter in ovs_execute_actions to implement an upper bound of 5 recursions. Cc: Pravin Shelar Cc: Simon Horman Cc: Eric Dumazet Cc: Simon Horman Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- net/openvswitch/actions.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c index c88d0f2d3e01..2d59df521915 100644 --- a/net/openvswitch/actions.c +++ b/net/openvswitch/actions.c @@ -1160,17 +1160,26 @@ int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb, const struct sw_flow_actions *acts, struct sw_flow_key *key) { - int level = this_cpu_read(exec_actions_level); - int err; + static const int ovs_recursion_limit = 5; + int err, level; + + level = __this_cpu_inc_return(exec_actions_level); + if (unlikely(level > ovs_recursion_limit)) { + net_crit_ratelimited("ovs: recursion limit reached on datapath %s, probable configuration error\n", + ovs_dp_name(dp)); + kfree_skb(skb); + err = -ENETDOWN; + goto out; + } - this_cpu_inc(exec_actions_level); err = do_execute_actions(dp, skb, key, acts->actions, acts->actions_len); - if (!level) + if (level == 1) process_deferred_actions(dp); - this_cpu_dec(exec_actions_level); +out: + __this_cpu_dec(exec_actions_level); return err; }