4 files changed, 28 insertions, 8 deletions

diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c
index 38512a200db6..a1bcb0e17250 100644
--- a/net/rxrpc/af_rxrpc.c
+++ b/net/rxrpc/af_rxrpc.c
@@ -33,8 +33,6 @@ unsigned int rxrpc_debug; // = RXRPC_DEBUG_KPROTO;
 module_param_named(debug, rxrpc_debug, uint, S_IWUSR | S_IRUGO);
 MODULE_PARM_DESC(debug, "RxRPC debugging mask");
 
-static int sysctl_rxrpc_max_qlen __read_mostly = 10;
-
 static struct proto rxrpc_proto;
 static const struct proto_ops rxrpc_rpc_ops;
 
@@ -191,6 +189,7 @@ static int rxrpc_listen(struct socket *sock, int backlog)
 {
 	struct sock *sk = sock->sk;
 	struct rxrpc_sock *rx = rxrpc_sk(sk);
+	unsigned int max;
 	int ret;
 
 	_enter("%p,%d", rx, backlog);
@@ -201,17 +200,21 @@ static int rxrpc_listen(struct socket *sock, int backlog)
 	case RXRPC_UNBOUND:
 		ret = -EADDRNOTAVAIL;
 		break;
-	case RXRPC_CLIENT_UNBOUND:
-	case RXRPC_CLIENT_BOUND:
-	default:
-		ret = -EBUSY;
-		break;
 	case RXRPC_SERVER_BOUND:
 		ASSERT(rx->local != NULL);
+		max = READ_ONCE(rxrpc_max_backlog);
+		ret = -EINVAL;
+		if (backlog == INT_MAX)
+			backlog = max;
+		else if (backlog < 0 || backlog > max)
+			break;
 		sk->sk_max_ack_backlog = backlog;
 		rx->sk.sk_state = RXRPC_SERVER_LISTENING;
 		ret = 0;
 		break;
+	default:
+		ret = -EBUSY;
+		break;
 	}
 
 	release_sock(&rx->sk);
@@ -591,7 +594,7 @@ static int rxrpc_create(struct net *net, struct socket *sock, int protocol,
 	sock_init_data(sock, sk);
 	sk->sk_state		= RXRPC_UNBOUND;
 	sk->sk_write_space	= rxrpc_write_space;
-	sk->sk_max_ack_backlog	= sysctl_rxrpc_max_qlen;
+	sk->sk_max_ack_backlog	= 0;
 	sk->sk_destruct		= rxrpc_sock_destructor;
 
 	rx = rxrpc_sk(sk);
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index b89dcdcbc65a..f715cca767cd 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -641,6 +641,7 @@ extern const struct rxrpc_security rxrpc_no_security;
 /*
  * misc.c
  */
+extern unsigned int rxrpc_max_backlog __read_mostly;
 extern unsigned int rxrpc_requested_ack_delay;
 extern unsigned int rxrpc_soft_ack_delay;
 extern unsigned int rxrpc_idle_ack_delay;
diff --git a/net/rxrpc/misc.c b/net/rxrpc/misc.c
index 1afe9876e79f..bdc5e42fe600 100644
--- a/net/rxrpc/misc.c
+++ b/net/rxrpc/misc.c
@@ -15,6 +15,12 @@
 #include "ar-internal.h"
 
 /*
+ * The maximum listening backlog queue size that may be set on a socket by
+ * listen().
+ */
+unsigned int rxrpc_max_backlog __read_mostly = 10;
+
+/*
  * How long to wait before scheduling ACK generation after seeing a
  * packet with RXRPC_REQUEST_ACK set (in jiffies).
  */
diff --git a/net/rxrpc/sysctl.c b/net/rxrpc/sysctl.c
index d20ed575acf4..a99690a8a3da 100644
--- a/net/rxrpc/sysctl.c
+++ b/net/rxrpc/sysctl.c
@@ -18,6 +18,7 @@ static struct ctl_table_header *rxrpc_sysctl_reg_table;
 static const unsigned int zero = 0;
 static const unsigned int one = 1;
 static const unsigned int four = 4;
+static const unsigned int thirtytwo = 32;
 static const unsigned int n_65535 = 65535;
 static const unsigned int n_max_acks = RXRPC_MAXACKS;
 
@@ -100,6 +101,15 @@ static struct ctl_table rxrpc_sysctl_table[] = {
 
 	/* Non-time values */
 	{
+		.procname	= "max_backlog",
+		.data		= &rxrpc_max_backlog,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= (void *)&four,
+		.extra2		= (void *)&thirtytwo,
+	},
+	{
 		.procname	= "rx_window_size",
 		.data		= &rxrpc_rx_window_size,
 		.maxlen		= sizeof(unsigned int),