Subject: [PATCH v2 bpf 2/2] bpf, sockmap: sk_prot needs inuse_idx for proc stats

From: John Fastabend <[email-masked]>
Date: Thu, 1 Jul 2021 17:11:23 -0700

Proc socket stats use sk_prot->inuse_idx value to record inuse sock stats.
We currently do not set this correctly from sockmap side. The result is
reading sock stats '/proc/net/sockstat' gives incorrect values. The
socket counter is incremented correctly, but because we don't set the
counter correctly when we replace sk_prot we may omit the decrement.

Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: John Fastabend <[email-masked]>
---
 net/core/sock_map.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 60decd6420ca..016ea5460f8f 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -222,6 +222,9 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
 	struct bpf_prog *msg_parser = NULL;
 	struct sk_psock *psock;
 	int ret;
+#ifdef CONFIG_PROC_FS
+	int idx;
+#endif
 
 	/* Only sockets we can redirect into/from in BPF need to hold
 	 * refs to parser/verdict progs and have their sk_data_ready
@@ -293,9 +296,15 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
 	if (msg_parser)
 		psock_set_prog(&psock->progs.msg_parser, msg_parser);
 
+#ifdef CONFIG_PROC_FS
+	idx = sk->sk_prot->inuse_idx;
+#endif
 	ret = sock_map_init_proto(sk, psock);
 	if (ret < 0)
 		goto out_drop;
+#ifdef CONFIG_PROC_FS
+	sk->sk_prot->inuse_idx = idx;
+#endif
 
 	write_lock_bh(&sk->sk_callback_lock);
 	if (stream_parser && stream_verdict && !psock->saved_data_ready) {
-- 
2.25.1