| Message ID | 1453136628-9816-1-git-send-email-hannes@stressinduktion.org |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Hannes Frederic Sowa <hannes@stressinduktion.org> Date: Mon, 18 Jan 2016 18:03:48 +0100 > 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 <pshelar@ovn.org> > Cc: Simon Horman <simon.horman@netronome.com> > Cc: Eric Dumazet <eric.dumazet@gmail.com> > Cc: Simon Horman <simon.horman@netronome.com> > Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Applied, thanks Hannes.
diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c index c88d0f2d3e019b..2d59df52191574 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; }
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 <pshelar@ovn.org> Cc: Simon Horman <simon.horman@netronome.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Simon Horman <simon.horman@netronome.com> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> --- v2) added preemption guards v3) Pravin suggested to reuse the ovs_execute_actions counter which this patch does. Also only allow 5 recursions as suggested by Pravin. v4) added unlikely as suggested by Eric v5) removed preempt guards as brought up with Pravin and discussed with David Thanks to all reviewers! net/openvswitch/actions.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)