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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 <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>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
Hannes Frederic Sowa 2016-01-18 18:03:48 +01:00 committed by David S. Miller
parent 60a6531bfe
commit b064d0d88a
1 changed files with 14 additions and 5 deletions
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19
net/openvswitch/actions.c
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@ -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;
}