bpf: Sockmap/tls, push write_space updates through ulp updates

When sockmap sock with TLS enabled is removed we cleanup bpf/psock state
and call tcp_update_ulp() to push updates to TLS ULP on top. However, we
don't push the write_space callback up and instead simply overwrite the
op with the psock stored previous op. This may or may not be correct so
to ensure we don't overwrite the TLS write space hook pass this field to
the ULP and have it fixup the ctx.

This completes a previous fix that pushed the ops through to the ULP
but at the time missed doing this for write_space, presumably because
write_space TLS hook was added around the same time.

Fixes: 95fa1454 ("bpf: sockmap/tls, close can race with map free")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/bpf/20200111061206.8028-4-john.fastabend@gmail.com

include/linux/skmsg.h

@@ -359,17 +359,21 @@ static inline void sk_psock_restore_proto(struct sock *sk,
 					  struct sk_psock *psock)
 {
 	sk->sk_prot->unhash = psock->saved_unhash;
-	sk->sk_write_space = psock->saved_write_space;
 
 	if (psock->sk_proto) {
 		struct inet_connection_sock *icsk = inet_csk(sk);
 		bool has_ulp = !!icsk->icsk_ulp_data;
 
-		if (has_ulp)
-			tcp_update_ulp(sk, psock->sk_proto);
-		else
+		if (has_ulp) {
+			tcp_update_ulp(sk, psock->sk_proto,
+				       psock->saved_write_space);
+		} else {
 			sk->sk_prot = psock->sk_proto;
+			sk->sk_write_space = psock->saved_write_space;
+		}
 		psock->sk_proto = NULL;
+	} else {
+		sk->sk_write_space = psock->saved_write_space;
 	}
 }
 

include/net/tcp.h

@@ -2147,7 +2147,8 @@ struct tcp_ulp_ops {
 	/* initialize ulp */
 	int (*init)(struct sock *sk);
 	/* update ulp */
-	void (*update)(struct sock *sk, struct proto *p);
+	void (*update)(struct sock *sk, struct proto *p,
+		       void (*write_space)(struct sock *sk));
 	/* cleanup ulp */
 	void (*release)(struct sock *sk);
 	/* diagnostic */
@@ -2162,7 +2163,8 @@ void tcp_unregister_ulp(struct tcp_ulp_ops *type);
 int tcp_set_ulp(struct sock *sk, const char *name);
 void tcp_get_available_ulp(char *buf, size_t len);
 void tcp_cleanup_ulp(struct sock *sk);
-void tcp_update_ulp(struct sock *sk, struct proto *p);
+void tcp_update_ulp(struct sock *sk, struct proto *p,
+		    void (*write_space)(struct sock *sk));
 
 #define MODULE_ALIAS_TCP_ULP(name)				\
 	__MODULE_INFO(alias, alias_userspace, name);		\

net/ipv4/tcp_ulp.c

@@ -99,17 +99,19 @@ void tcp_get_available_ulp(char *buf, size_t maxlen)
 	rcu_read_unlock();
 }
 
-void tcp_update_ulp(struct sock *sk, struct proto *proto)
+void tcp_update_ulp(struct sock *sk, struct proto *proto,
+		    void (*write_space)(struct sock *sk))
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
 	if (!icsk->icsk_ulp_ops) {
+		sk->sk_write_space = write_space;
 		sk->sk_prot = proto;
 		return;
 	}
 
 	if (icsk->icsk_ulp_ops->update)
-		icsk->icsk_ulp_ops->update(sk, proto);
+		icsk->icsk_ulp_ops->update(sk, proto, write_space);
 }
 
 void tcp_cleanup_ulp(struct sock *sk)

net/tls/tls_main.c

@@ -732,15 +732,19 @@ static int tls_init(struct sock *sk)
 	return rc;
 }
 
-static void tls_update(struct sock *sk, struct proto *p)
+static void tls_update(struct sock *sk, struct proto *p,
+		       void (*write_space)(struct sock *sk))
 {
 	struct tls_context *ctx;
 
 	ctx = tls_get_ctx(sk);
-	if (likely(ctx))
+	if (likely(ctx)) {
+		ctx->sk_write_space = write_space;
 		ctx->sk_proto = p;
-	else
+	} else {
 		sk->sk_prot = p;
+		sk->sk_write_space = write_space;
+	}
 }
 
 static int tls_get_info(const struct sock *sk, struct sk_buff *skb)