[PATCH bpf 1/3] bpf, sockmap: Fix update element with same

[Michal Luczaj]

Consider a sockmap entry being updated with the same socket:

        osk = stab->sks[idx];
        sock_map_add_link(psock, link, map, &stab->sks[idx]);
        stab->sks[idx] = sk;
        if (osk)
                sock_map_unref(osk, &stab->sks[idx]);

Due to sock_map_unref(), which invokes sock_map_del_link(), all the psock's
links for stab->sks[idx] are torn:

        list_for_each_entry_safe(link, tmp, &psock->link, list) {
                if (link->link_raw == link_raw) {
                        ...
                        list_del(&link->list);
                        sk_psock_free_link(link);
                }
        }

And that includes the new link sock_map_add_link() added just before the
unref.

This results in a sockmap holding a socket, but without the respective
link. This in turn means that close(sock) won't trigger the cleanup, i.e. a
closed socket will not be automatically removed from the sockmap.

Stop tearing the links when a matching link_raw is found.

Signed-off-by: Michal Luczaj <m...@rbox.co>
---
 net/core/sock_map.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 
78347d7d25ef31525f8ec0a755a18e5793ad92c0..20b348b1964a10a1b0bfbe1a90a4a4cd99715b81
 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -159,6 +159,7 @@ static void sock_map_del_link(struct sock *sk,
                                verdict_stop = true;
                        list_del(&link->list);
                        sk_psock_free_link(link);
+                       break;
                }
        }
        spin_unlock_bh(&psock->link_lock);

-- 
2.46.2