vsock: fix recursive ->recvmsg calls

After a vsock socket has been added to a BPF sockmap, its prot->recvmsg
has been replaced with vsock_bpf_recvmsg(). Thus the following
recursiion could happen:

vsock_bpf_recvmsg()
 -> __vsock_recvmsg()
  -> vsock_connectible_recvmsg()
   -> prot->recvmsg()
    -> vsock_bpf_recvmsg() again

We need to fix it by calling the original ->recvmsg() without any BPF
sockmap logic in __vsock_recvmsg().

Fixes: 634f1a71 ("vsock: support sockmap")
Reported-by: syzbot+bdb4bd87b5e22058e2a4@syzkaller.appspotmail.com
Tested-by: syzbot+bdb4bd87b5e22058e2a4@syzkaller.appspotmail.com
Cc: Bobby Eshleman <bobby.eshleman@bytedance.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20240812022153.86512-1-xiyou.wangcong@gmail.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

include/net/af_vsock.h

@@ -230,8 +230,12 @@ struct vsock_tap {
 int vsock_add_tap(struct vsock_tap *vt);
 int vsock_remove_tap(struct vsock_tap *vt);
 void vsock_deliver_tap(struct sk_buff *build_skb(void *opaque), void *opaque);
+int __vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
+				int flags);
 int vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 			      int flags);
+int __vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
+			  size_t len, int flags);
 int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
 			size_t len, int flags);
 

net/vmw_vsock/af_vsock.c

@@ -1270,25 +1270,28 @@ static int vsock_dgram_connect(struct socket *sock,
 	return err;
 }
 
+int __vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
+			  size_t len, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct vsock_sock *vsk = vsock_sk(sk);
+
+	return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
+}
+
 int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
 			size_t len, int flags)
 {
 #ifdef CONFIG_BPF_SYSCALL
+	struct sock *sk = sock->sk;
 	const struct proto *prot;
-#endif
-	struct vsock_sock *vsk;
-	struct sock *sk;
 
-	sk = sock->sk;
-	vsk = vsock_sk(sk);
-
-#ifdef CONFIG_BPF_SYSCALL
 	prot = READ_ONCE(sk->sk_prot);
 	if (prot != &vsock_proto)
 		return prot->recvmsg(sk, msg, len, flags, NULL);
 #endif
 
-	return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
+	return __vsock_dgram_recvmsg(sock, msg, len, flags);
 }
 EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
 
@@ -2174,15 +2177,12 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
 }
 
 int
-vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
-			  int flags)
+__vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
+			    int flags)
 {
 	struct sock *sk;
 	struct vsock_sock *vsk;
 	const struct vsock_transport *transport;
-#ifdef CONFIG_BPF_SYSCALL
-	const struct proto *prot;
-#endif
 	int err;
 
 	sk = sock->sk;
@@ -2233,14 +2233,6 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 		goto out;
 	}
 
-#ifdef CONFIG_BPF_SYSCALL
-	prot = READ_ONCE(sk->sk_prot);
-	if (prot != &vsock_proto) {
-		release_sock(sk);
-		return prot->recvmsg(sk, msg, len, flags, NULL);
-	}
-#endif
-
 	if (sk->sk_type == SOCK_STREAM)
 		err = __vsock_stream_recvmsg(sk, msg, len, flags);
 	else
@@ -2250,6 +2242,22 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	release_sock(sk);
 	return err;
 }
+
+int
+vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
+			  int flags)
+{
+#ifdef CONFIG_BPF_SYSCALL
+	struct sock *sk = sock->sk;
+	const struct proto *prot;
+
+	prot = READ_ONCE(sk->sk_prot);
+	if (prot != &vsock_proto)
+		return prot->recvmsg(sk, msg, len, flags, NULL);
+#endif
+
+	return __vsock_connectible_recvmsg(sock, msg, len, flags);
+}
 EXPORT_SYMBOL_GPL(vsock_connectible_recvmsg);
 
 static int vsock_set_rcvlowat(struct sock *sk, int val)

net/vmw_vsock/vsock_bpf.c

@@ -64,9 +64,9 @@ static int __vsock_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int
 	int err;
 
 	if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)
-		err = vsock_connectible_recvmsg(sock, msg, len, flags);
+		err = __vsock_connectible_recvmsg(sock, msg, len, flags);
 	else if (sk->sk_type == SOCK_DGRAM)
-		err = vsock_dgram_recvmsg(sock, msg, len, flags);
+		err = __vsock_dgram_recvmsg(sock, msg, len, flags);
 	else
 		err = -EPROTOTYPE;