[bpf PATCH v2 2/2] bpf: sockmap only allow ESTABLISHED sock state

[John Fastabend <john.fastabend@gmail.com>]

Per the note in the TLS ULP (which is actually a generic statement
regarding ULPs)

 /* The TLS ulp is currently supported only for TCP sockets
  * in ESTABLISHED state.
  * Supporting sockets in LISTEN state will require us
  * to modify the accept implementation to clone rather then
  * share the ulp context.
  */

After this patch we only allow socks that are in ESTABLISHED state or
are being added via a sock_ops event that is transitioning into an
ESTABLISHED state. By allowing sock_ops events we allow users to
manage sockmaps directly from sock ops programs. The two supported
sock_ops ops are BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB and
BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB.

Also tested with 'netserver -6' and 'netperf -H [IPv6]' as well as
'netperf -H [IPv4]'.

Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
 kernel/bpf/sockmap.c |   32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index fa9b7f3..4921fb7 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -1956,8 +1956,12 @@ static int sock_map_update_elem(struct bpf_map *map,
 		return -EINVAL;
 	}
 
+	/* ULPs are currently supported only for TCP sockets in ESTABLISHED
+	 * state.
+	 */
 	if (skops.sk->sk_type != SOCK_STREAM ||
-	    skops.sk->sk_protocol != IPPROTO_TCP) {
+	    skops.sk->sk_protocol != IPPROTO_TCP ||
+	    skops.sk->sk_state != TCP_ESTABLISHED) {
 		fput(socket->file);
 		return -EOPNOTSUPP;
 	}
@@ -2318,6 +2322,16 @@ static int sock_hash_update_elem(struct bpf_map *map,
 		return -EINVAL;
 	}
 
+	/* ULPs are currently supported only for TCP sockets in ESTABLISHED
+	 * state.
+	 */
+	if (skops.sk->sk_type != SOCK_STREAM ||
+	    skops.sk->sk_protocol != IPPROTO_TCP ||
+	    skops.sk->sk_state != TCP_ESTABLISHED) {
+		fput(socket->file);
+		return -EOPNOTSUPP;
+	}
+
 	err = sock_hash_ctx_update_elem(&skops, map, key, flags);
 	fput(socket->file);
 	return err;
@@ -2403,10 +2417,23 @@ struct sock  *__sock_hash_lookup_elem(struct bpf_map *map, void *key)
 	.map_delete_elem = sock_hash_delete_elem,
 };
 
+static bool bpf_is_valid_sock(struct bpf_sock_ops_kern *ops)
+{
+	return ops->op == BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB ||
+	       ops->op == BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB;
+}
+
 BPF_CALL_4(bpf_sock_map_update, struct bpf_sock_ops_kern *, bpf_sock,
 	   struct bpf_map *, map, void *, key, u64, flags)
 {
 	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	/* ULPs are currently supported only for TCP sockets in ESTABLISHED
+	 * state. This checks that the sock ops triggering the update is
+	 * one indicating we are (or will be soon) in an ESTABLISHED state.
+	 */
+	if (!bpf_is_valid_sock(bpf_sock))
+		return -EOPNOTSUPP;
 	return sock_map_ctx_update_elem(bpf_sock, map, key, flags);
 }
 
@@ -2425,6 +2452,9 @@ struct sock  *__sock_hash_lookup_elem(struct bpf_map *map, void *key)
 	   struct bpf_map *, map, void *, key, u64, flags)
 {
 	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	if (!bpf_is_valid_sock(bpf_sock))
+		return -EOPNOTSUPP;
 	return sock_hash_ctx_update_elem(bpf_sock, map, key, flags);
 }