When there are no references to struct net left, that is check_net(net) is
false, we don't need to synchronize updates to flow_dissector prog with BPF
prog attach/detach callbacks. That allows us to pull locking up from the
shared detach routine and into the bpf prog detach callback.
Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
---
net/core/flow_dissector.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 5dceed467f64..73cc085dc2b7 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -164,22 +164,26 @@ static int flow_dissector_bpf_prog_detach(struct net *net)
{
struct bpf_prog *attached;
- mutex_lock(&flow_dissector_mutex);
+ /* No need for update-side lock when net is going away. */
attached = rcu_dereference_protected(net->flow_dissector_prog,
+ !check_net(net) ||
lockdep_is_held(&flow_dissector_mutex));
- if (!attached) {
- mutex_unlock(&flow_dissector_mutex);
+ if (!attached)
return -ENOENT;
- }
RCU_INIT_POINTER(net->flow_dissector_prog, NULL);
bpf_prog_put(attached);
- mutex_unlock(&flow_dissector_mutex);
return 0;
}
int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr)
{
- return flow_dissector_bpf_prog_detach(current->nsproxy->net_ns);
+ int ret;
+
+ mutex_lock(&flow_dissector_mutex);
+ ret = flow_dissector_bpf_prog_detach(current->nsproxy->net_ns);
+ mutex_unlock(&flow_dissector_mutex);
+
+ return ret;
}
static void __net_exit flow_dissector_pernet_pre_exit(struct net *net)
--
2.25.4
