[bpf PATCH v2 4/6] bpf: sockmap, synchronize_rcu before free'ing map

[John Fastabend]

We need to have a synchronize_rcu before free'ing the sockmap because
any outstanding psock references will have a pointer to the map and
when they use this could trigger a use after free.

Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: John Fastabend <john.fastab...@gmail.com>
---
 net/core/sock_map.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 28702f2e9a4a..56bcabe7c2f2 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -247,6 +247,8 @@ static void sock_map_free(struct bpf_map *map)
        raw_spin_unlock_bh(&stab->lock);
        rcu_read_unlock();
 
+       synchronize_rcu();
+
        bpf_map_area_free(stab->sks);
        kfree(stab);
 }