bpf: sockmap remove duplicate queue free

[ Upstream commit c42253cc ]

In tcp bpf remove we free the cork list and purge the ingress msg
list. However we do this before the ref count reaches zero so it
could be possible some other access is in progress. In this case
(tcp close and/or tcp_unhash) we happen to also hold the sock
lock so no path exists but lets fix it otherwise it is extremely
fragile and breaks the reference counting rules. Also we already
check the cork list and ingress msg queue and free them once the
ref count reaches zero so its wasteful to check twice.

Fixes: 604326b4 ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/ipv4/tcp_bpf.c

@@ -528,8 +528,6 @@ static void tcp_bpf_remove(struct sock *sk, struct sk_psock *psock)
 {
 	struct sk_psock_link *link;
 
-	sk_psock_cork_free(psock);
-	__sk_psock_purge_ingress_msg(psock);
 	while ((link = sk_psock_link_pop(psock))) {
 		sk_psock_unlink(sk, link);
 		sk_psock_free_link(link);