[Bluetooth] Fix L2CAP configuration parameter handling

The L2CAP configuration parameter handling was missing the support
for rejecting unknown options. The capability to reject unknown
options is mandatory since the Bluetooth 1.2 specification. This
patch implements its and also simplifies the parameter parsing.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/l2cap.h

@@ -129,8 +129,10 @@ struct l2cap_conf_rsp {
 	__u8       data[0];
 } __attribute__ ((packed));
 
-#define L2CAP_CONF_SUCCESS	0x00
-#define L2CAP_CONF_UNACCEPT	0x01
+#define L2CAP_CONF_SUCCESS	0x0000
+#define L2CAP_CONF_UNACCEPT	0x0001
+#define L2CAP_CONF_REJECT	0x0002
+#define L2CAP_CONF_UNKNOWN	0x0003
 
 struct l2cap_conf_opt {
 	__u8       type;
@@ -215,6 +217,8 @@ struct l2cap_pinfo {
 
 	__u32		link_mode;
 
+	__u8		conf_req[64];
+	__u8		conf_len;
 	__u8		conf_state;
 	__u8		conf_retry;
 	__u16		conf_mtu;

net/bluetooth/l2cap.c

@@ -507,6 +507,7 @@ static void l2cap_sock_init(struct sock *sk, struct sock *parent)
 	}
 
 	/* Default config options */
+	pi->conf_len = 0;
 	pi->conf_mtu = L2CAP_DEFAULT_MTU;
 	pi->flush_to = L2CAP_DEFAULT_FLUSH_TO;
 }
@@ -1271,42 +1272,6 @@ static inline int l2cap_get_conf_opt(void **ptr, int *type, int *olen, unsigned
 	return len;
 }
 
-static inline void l2cap_parse_conf_req(struct sock *sk, void *data, int len)
-{
-	int type, hint, olen;
-	unsigned long val;
-	void *ptr = data;
-
-	BT_DBG("sk %p len %d", sk, len);
-
-	while (len >= L2CAP_CONF_OPT_SIZE) {
-		len -= l2cap_get_conf_opt(&ptr, &type, &olen, &val);
-
-		hint  = type & 0x80;
-		type &= 0x7f;
-
-		switch (type) {
-		case L2CAP_CONF_MTU:
-			l2cap_pi(sk)->conf_mtu = val;
-			break;
-
-		case L2CAP_CONF_FLUSH_TO:
-			l2cap_pi(sk)->flush_to = val;
-			break;
-
-		case L2CAP_CONF_QOS:
-			break;
-
-		default:
-			if (hint)
-				break;
-
-			/* FIXME: Reject unknown option */
-			break;
-		}
-	}
-}
-
 static void l2cap_add_conf_opt(void **ptr, u8 type, u8 len, unsigned long val)
 {
 	struct l2cap_conf_opt *opt = *ptr;
@@ -1358,39 +1323,75 @@ static int l2cap_build_conf_req(struct sock *sk, void *data)
 	return ptr - data;
 }
 
-static inline int l2cap_conf_output(struct sock *sk, void **ptr)
+static int l2cap_parse_conf_req(struct sock *sk, void *data)
 {
 	struct l2cap_pinfo *pi = l2cap_pi(sk);
-	int result = 0;
+	struct l2cap_conf_rsp *rsp = data;
+	void *ptr = rsp->data;
+	void *req = pi->conf_req;
+	int len = pi->conf_len;
+	int type, hint, olen;
+	unsigned long val;
+	u16 result = L2CAP_CONF_SUCCESS;
 
-	/* Configure output options and let the other side know
-	 * which ones we don't like. */
-	if (pi->conf_mtu < pi->omtu)
-		result = L2CAP_CONF_UNACCEPT;
-	else
-		pi->omtu = pi->conf_mtu;
+	BT_DBG("sk %p", sk);
+
+	while (len >= L2CAP_CONF_OPT_SIZE) {
+		len -= l2cap_get_conf_opt(&req, &type, &olen, &val);
 
-	l2cap_add_conf_opt(ptr, L2CAP_CONF_MTU, 2, pi->omtu);
+		hint  = type & 0x80;
+		type &= 0x7f;
+
+		switch (type) {
+		case L2CAP_CONF_MTU:
+			pi->conf_mtu = val;
+			break;
+
+		case L2CAP_CONF_FLUSH_TO:
+			pi->flush_to = val;
+			break;
+
+		case L2CAP_CONF_QOS:
+			break;
+
+		default:
+			if (hint)
+				break;
+
+			result = L2CAP_CONF_UNKNOWN;
+			*((u8 *) ptr++) = type;
+			break;
+		}
+	}
+
+	if (result == L2CAP_CONF_SUCCESS) {
+		/* Configure output options and let the other side know
+		 * which ones we don't like. */
+
+		if (pi->conf_mtu < pi->omtu)
+			result = L2CAP_CONF_UNACCEPT;
+		else
+			pi->omtu = pi->conf_mtu;
+
+		l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, pi->omtu);
+	}
 
-	BT_DBG("sk %p result %d", sk, result);
-	return result;
+	rsp->scid   = cpu_to_le16(pi->dcid);
+	rsp->result = cpu_to_le16(result);
+	rsp->flags  = cpu_to_le16(0x0000);
+
+	return ptr - data;
 }
 
-static int l2cap_build_conf_rsp(struct sock *sk, void *data, int *result)
+static int l2cap_build_conf_rsp(struct sock *sk, void *data, u16 result, u16 flags)
 {
 	struct l2cap_conf_rsp *rsp = data;
 	void *ptr = rsp->data;
-	u16 flags = 0;
-
-	BT_DBG("sk %p complete %d", sk, result ? 1 : 0);
 
-	if (result)
-		*result = l2cap_conf_output(sk, &ptr);
-	else
-		flags = 0x0001;
+	BT_DBG("sk %p", sk);
 
 	rsp->scid   = cpu_to_le16(l2cap_pi(sk)->dcid);
-	rsp->result = cpu_to_le16(result ? *result : 0);
+	rsp->result = cpu_to_le16(result);
 	rsp->flags  = cpu_to_le16(flags);
 
 	return ptr - data;
@@ -1535,7 +1536,7 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 	u16 dcid, flags;
 	u8 rsp[64];
 	struct sock *sk;
-	int result;
+	int len;
 
 	dcid  = __le16_to_cpu(req->dcid);
 	flags = __le16_to_cpu(req->flags);
@@ -1548,25 +1549,40 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 	if (sk->sk_state == BT_DISCONN)
 		goto unlock;
 
-	l2cap_parse_conf_req(sk, req->data, cmd->len - sizeof(*req));
+	/* Reject if config buffer is too small. */
+	len = cmd->len - sizeof(*req);
+	if (l2cap_pi(sk)->conf_len + len > sizeof(l2cap_pi(sk)->conf_req)) {
+		l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP,
+				l2cap_build_conf_rsp(sk, rsp,
+					L2CAP_CONF_REJECT, flags), rsp);
+		goto unlock;
+	}
+
+	/* Store config. */
+	memcpy(l2cap_pi(sk)->conf_req + l2cap_pi(sk)->conf_len, req->data, len);
+	l2cap_pi(sk)->conf_len += len;
 
 	if (flags & 0x0001) {
 		/* Incomplete config. Send empty response. */
 		l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP,
-				l2cap_build_conf_rsp(sk, rsp, NULL), rsp);
+				l2cap_build_conf_rsp(sk, rsp,
+					L2CAP_CONF_SUCCESS, 0x0001), rsp);
 		goto unlock;
 	}
 
 	/* Complete config. */
-	l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP,
-			l2cap_build_conf_rsp(sk, rsp, &result), rsp);
-
-	if (result)
+	len = l2cap_parse_conf_req(sk, rsp);
+	if (len < 0)
 		goto unlock;
 
-	/* Output config done */
+	l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP, len, rsp);
+
+	/* Output config done. */
 	l2cap_pi(sk)->conf_state |= L2CAP_CONF_OUTPUT_DONE;
 
+	/* Reset config buffer. */
+	l2cap_pi(sk)->conf_len = 0;
+
 	if (l2cap_pi(sk)->conf_state & L2CAP_CONF_INPUT_DONE) {
 		sk->sk_state = BT_CONNECTED;
 		l2cap_chan_ready(sk);