kcm: Fix locking issue

Lock the lower socket in kcm_unattach. Release during call to strp_done
since that function cancels the RX timers and work queue with sync.

Also added some status information in psock reporting.
Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/kcm/kcmproc.c

@@ -173,14 +173,24 @@ static void kcm_format_psock(struct kcm_psock *psock, struct seq_file *seq,
 	if (psock->strp.rx_stopped)
 		seq_puts(seq, "RxStop ");
 
-	if (psock->strp.rx_paused)
-		seq_puts(seq, "RxPause ");
-
 	if (psock->tx_kcm)
 		seq_printf(seq, "Rsvd-%d ", psock->tx_kcm->index);
 
+	if (!psock->strp.rx_paused && !psock->ready_rx_msg) {
+		if (psock->sk->sk_receive_queue.qlen) {
+			if (psock->strp.rx_need_bytes)
+				seq_printf(seq, "RxWait=%u ",
+					   psock->strp.rx_need_bytes);
+			else
+				seq_printf(seq, "RxWait ");
+		}
+	} else  {
+		if (psock->strp.rx_paused)
+			seq_puts(seq, "RxPause ");
+
 		if (psock->ready_rx_msg)
 			seq_puts(seq, "RdyRx ");
+	}
 
 	seq_puts(seq, "\n");
 }

net/kcm/kcmsock.c

@@ -1477,12 +1477,13 @@ static int kcm_attach_ioctl(struct socket *sock, struct kcm_attach *info)
 	return err;
 }
 
-/* Lower socket lock held */
 static void kcm_unattach(struct kcm_psock *psock)
 {
 	struct sock *csk = psock->sk;
 	struct kcm_mux *mux = psock->mux;
 
+	lock_sock(csk);
+
 	/* Stop getting callbacks from TCP socket. After this there should
 	 * be no way to reserve a kcm for this psock.
 	 */
@@ -1514,7 +1515,10 @@ static void kcm_unattach(struct kcm_psock *psock)
 
 	write_unlock_bh(&csk->sk_callback_lock);
 
+	/* Call strp_done without sock lock */
+	release_sock(csk);
 	strp_done(&psock->strp);
+	lock_sock(csk);
 
 	bpf_prog_put(psock->bpf_prog);
 
@@ -1564,6 +1568,8 @@ static void kcm_unattach(struct kcm_psock *psock)
 		fput(csk->sk_socket->file);
 		kmem_cache_free(kcm_psockp, psock);
 	}
+
+	release_sock(csk);
 }
 
 static int kcm_unattach_ioctl(struct socket *sock, struct kcm_unattach *info)
@@ -1749,11 +1755,8 @@ static void release_mux(struct kcm_mux *mux)
 	/* Release psocks */
 	list_for_each_entry_safe(psock, tmp_psock,
 				 &mux->psocks, psock_list) {
-		if (!WARN_ON(psock->unattaching)) {
-			lock_sock(psock->strp.sk);
+		if (!WARN_ON(psock->unattaching))
 			kcm_unattach(psock);
-			release_sock(psock->strp.sk);
-		}
 	}
 
 	if (WARN_ON(mux->psocks_cnt))