[PATCH 3.16 138/192] Bluetooth: Properly check L2CAP config option output buffer length

[Ben Hutchings <ben@decadent.org.uk>]

3.16.49-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Seri <ben@armis.com>

commit e860d2c904d1a9f38a24eb44c9f34b8f915a6ea3 upstream.

Validate the output buffer length for L2CAP config requests and responses
to avoid overflowing the stack buffer used for building the option blocks.

Signed-off-by: Ben Seri <ben@armis.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 net/bluetooth/l2cap_core.c | 80 +++++++++++++++++++++++++---------------------
 1 file changed, 43 insertions(+), 37 deletions(-)

--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -59,7 +59,7 @@ static struct sk_buff *l2cap_build_cmd(s
 				       u8 code, u8 ident, u16 dlen, void *data);
 static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
 			   void *data);
-static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data);
+static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data, size_t data_size);
 static void l2cap_send_disconn_req(struct l2cap_chan *chan, int err);
 
 static void l2cap_tx(struct l2cap_chan *chan, struct l2cap_ctrl *control,
@@ -1401,7 +1401,7 @@ static void l2cap_conn_start(struct l2ca
 
 			set_bit(CONF_REQ_SENT, &chan->conf_state);
 			l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
-				       l2cap_build_conf_req(chan, buf), buf);
+				       l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
 			chan->num_conf_req++;
 		}
 
@@ -2978,12 +2978,15 @@ static inline int l2cap_get_conf_opt(voi
 	return len;
 }
 
-static void l2cap_add_conf_opt(void **ptr, u8 type, u8 len, unsigned long val)
+static void l2cap_add_conf_opt(void **ptr, u8 type, u8 len, unsigned long val, size_t size)
 {
 	struct l2cap_conf_opt *opt = *ptr;
 
 	BT_DBG("type 0x%2.2x len %u val 0x%lx", type, len, val);
 
+	if (size < L2CAP_CONF_OPT_SIZE + len)
+		return;
+
 	opt->type = type;
 	opt->len  = len;
 
@@ -3008,7 +3011,7 @@ static void l2cap_add_conf_opt(void **pt
 	*ptr += L2CAP_CONF_OPT_SIZE + len;
 }
 
-static void l2cap_add_opt_efs(void **ptr, struct l2cap_chan *chan)
+static void l2cap_add_opt_efs(void **ptr, struct l2cap_chan *chan, size_t size)
 {
 	struct l2cap_conf_efs efs;
 
@@ -3036,7 +3039,7 @@ static void l2cap_add_opt_efs(void **ptr
 	}
 
 	l2cap_add_conf_opt(ptr, L2CAP_CONF_EFS, sizeof(efs),
-			   (unsigned long) &efs);
+			   (unsigned long) &efs, size);
 }
 
 static void l2cap_ack_timeout(struct work_struct *work)
@@ -3180,11 +3183,12 @@ static inline void l2cap_txwin_setup(str
 	chan->ack_win = chan->tx_win;
 }
 
-static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data)
+static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data, size_t data_size)
 {
 	struct l2cap_conf_req *req = data;
 	struct l2cap_conf_rfc rfc = { .mode = chan->mode };
 	void *ptr = req->data;
+	void *endptr = data + data_size;
 	u16 size;
 
 	BT_DBG("chan %p", chan);
@@ -3209,7 +3213,7 @@ static int l2cap_build_conf_req(struct l
 
 done:
 	if (chan->imtu != L2CAP_DEFAULT_MTU)
-		l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu);
+		l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu, endptr - ptr);
 
 	switch (chan->mode) {
 	case L2CAP_MODE_BASIC:
@@ -3225,7 +3229,7 @@ done:
 		rfc.max_pdu_size    = 0;
 
 		l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
-				   (unsigned long) &rfc);
+				   (unsigned long) &rfc, endptr - ptr);
 		break;
 
 	case L2CAP_MODE_ERTM:
@@ -3245,21 +3249,21 @@ done:
 				       L2CAP_DEFAULT_TX_WINDOW);
 
 		l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
-				   (unsigned long) &rfc);
+				   (unsigned long) &rfc, endptr - ptr);
 
 		if (test_bit(FLAG_EFS_ENABLE, &chan->flags))
-			l2cap_add_opt_efs(&ptr, chan);
+			l2cap_add_opt_efs(&ptr, chan, endptr - ptr);
 
 		if (test_bit(FLAG_EXT_CTRL, &chan->flags))
 			l2cap_add_conf_opt(&ptr, L2CAP_CONF_EWS, 2,
-					   chan->tx_win);
+					   chan->tx_win, endptr - ptr);
 
 		if (chan->conn->feat_mask & L2CAP_FEAT_FCS)
 			if (chan->fcs == L2CAP_FCS_NONE ||
 			    test_bit(CONF_RECV_NO_FCS, &chan->conf_state)) {
 				chan->fcs = L2CAP_FCS_NONE;
 				l2cap_add_conf_opt(&ptr, L2CAP_CONF_FCS, 1,
-						   chan->fcs);
+						   chan->fcs, endptr - ptr);
 			}
 		break;
 
@@ -3277,17 +3281,17 @@ done:
 		rfc.max_pdu_size = cpu_to_le16(size);
 
 		l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
-				   (unsigned long) &rfc);
+				   (unsigned long) &rfc, endptr - ptr);
 
 		if (test_bit(FLAG_EFS_ENABLE, &chan->flags))
-			l2cap_add_opt_efs(&ptr, chan);
+			l2cap_add_opt_efs(&ptr, chan, endptr - ptr);
 
 		if (chan->conn->feat_mask & L2CAP_FEAT_FCS)
 			if (chan->fcs == L2CAP_FCS_NONE ||
 			    test_bit(CONF_RECV_NO_FCS, &chan->conf_state)) {
 				chan->fcs = L2CAP_FCS_NONE;
 				l2cap_add_conf_opt(&ptr, L2CAP_CONF_FCS, 1,
-						   chan->fcs);
+						   chan->fcs, endptr - ptr);
 			}
 		break;
 	}
@@ -3298,10 +3302,11 @@ done:
 	return ptr - data;
 }
 
-static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data)
+static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data_size)
 {
 	struct l2cap_conf_rsp *rsp = data;
 	void *ptr = rsp->data;
+	void *endptr = data + data_size;
 	void *req = chan->conf_req;
 	int len = chan->conf_len;
 	int type, hint, olen;
@@ -3403,7 +3408,7 @@ done:
 			return -ECONNREFUSED;
 
 		l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
-				   (unsigned long) &rfc);
+				   (unsigned long) &rfc, endptr - ptr);
 	}
 
 	if (result == L2CAP_CONF_SUCCESS) {
@@ -3416,7 +3421,7 @@ done:
 			chan->omtu = mtu;
 			set_bit(CONF_MTU_DONE, &chan->conf_state);
 		}
-		l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->omtu);
+		l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->omtu, endptr - ptr);
 
 		if (remote_efs) {
 			if (chan->local_stype != L2CAP_SERV_NOTRAFIC &&
@@ -3430,7 +3435,7 @@ done:
 
 				l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS,
 						   sizeof(efs),
-						   (unsigned long) &efs);
+						   (unsigned long) &efs, endptr - ptr);
 			} else {
 				/* Send PENDING Conf Rsp */
 				result = L2CAP_CONF_PENDING;
@@ -3463,7 +3468,7 @@ done:
 			set_bit(CONF_MODE_DONE, &chan->conf_state);
 
 			l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
-					   sizeof(rfc), (unsigned long) &rfc);
+					   sizeof(rfc), (unsigned long) &rfc, endptr - ptr);
 
 			if (test_bit(FLAG_EFS_ENABLE, &chan->flags)) {
 				chan->remote_id = efs.id;
@@ -3477,7 +3482,7 @@ done:
 					le32_to_cpu(efs.sdu_itime);
 				l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS,
 						   sizeof(efs),
-						   (unsigned long) &efs);
+						   (unsigned long) &efs, endptr - ptr);
 			}
 			break;
 
@@ -3491,7 +3496,7 @@ done:
 			set_bit(CONF_MODE_DONE, &chan->conf_state);
 
 			l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
-					   (unsigned long) &rfc);
+					   (unsigned long) &rfc, endptr - ptr);
 
 			break;
 
@@ -3513,10 +3518,11 @@ done:
 }
 
 static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len,
-				void *data, u16 *result)
+				void *data, size_t size, u16 *result)
 {
 	struct l2cap_conf_req *req = data;
 	void *ptr = req->data;
+	void *endptr = data + size;
 	int type, olen;
 	unsigned long val;
 	struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_BASIC };
@@ -3534,13 +3540,13 @@ static int l2cap_parse_conf_rsp(struct l
 				chan->imtu = L2CAP_DEFAULT_MIN_MTU;
 			} else
 				chan->imtu = val;
-			l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu);
+			l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu, endptr - ptr);
 			break;
 
 		case L2CAP_CONF_FLUSH_TO:
 			chan->flush_to = val;
 			l2cap_add_conf_opt(&ptr, L2CAP_CONF_FLUSH_TO,
-					   2, chan->flush_to);
+					   2, chan->flush_to, endptr - ptr);
 			break;
 
 		case L2CAP_CONF_RFC:
@@ -3554,13 +3560,13 @@ static int l2cap_parse_conf_rsp(struct l
 			chan->fcs = 0;
 
 			l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
-					   sizeof(rfc), (unsigned long) &rfc);
+					   sizeof(rfc), (unsigned long) &rfc, endptr - ptr);
 			break;
 
 		case L2CAP_CONF_EWS:
 			chan->ack_win = min_t(u16, val, chan->ack_win);
 			l2cap_add_conf_opt(&ptr, L2CAP_CONF_EWS, 2,
-					   chan->tx_win);
+					   chan->tx_win, endptr - ptr);
 			break;
 
 		case L2CAP_CONF_EFS:
@@ -3573,7 +3579,7 @@ static int l2cap_parse_conf_rsp(struct l
 				return -ECONNREFUSED;
 
 			l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS, sizeof(efs),
-					   (unsigned long) &efs);
+					   (unsigned long) &efs, endptr - ptr);
 			break;
 
 		case L2CAP_CONF_FCS:
@@ -3678,7 +3684,7 @@ void __l2cap_connect_rsp_defer(struct l2
 		return;
 
 	l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
-		       l2cap_build_conf_req(chan, buf), buf);
+		       l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
 	chan->num_conf_req++;
 }
 
@@ -3885,7 +3891,7 @@ sendresp:
 		u8 buf[128];
 		set_bit(CONF_REQ_SENT, &chan->conf_state);
 		l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
-			       l2cap_build_conf_req(chan, buf), buf);
+			       l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
 		chan->num_conf_req++;
 	}
 
@@ -3965,7 +3971,7 @@ static int l2cap_connect_create_rsp(stru
 			break;
 
 		l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
-			       l2cap_build_conf_req(chan, req), req);
+			       l2cap_build_conf_req(chan, req, sizeof(req)), req);
 		chan->num_conf_req++;
 		break;
 
@@ -4077,7 +4083,7 @@ static inline int l2cap_config_req(struc
 	}
 
 	/* Complete config. */
-	len = l2cap_parse_conf_req(chan, rsp);
+	len = l2cap_parse_conf_req(chan, rsp, sizeof(rsp));
 	if (len < 0) {
 		l2cap_send_disconn_req(chan, ECONNRESET);
 		goto unlock;
@@ -4111,7 +4117,7 @@ static inline int l2cap_config_req(struc
 	if (!test_and_set_bit(CONF_REQ_SENT, &chan->conf_state)) {
 		u8 buf[64];
 		l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
-			       l2cap_build_conf_req(chan, buf), buf);
+			       l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
 		chan->num_conf_req++;
 	}
 
@@ -4171,7 +4177,7 @@ static inline int l2cap_config_rsp(struc
 			char buf[64];
 
 			len = l2cap_parse_conf_rsp(chan, rsp->data, len,
-						   buf, &result);
+						   buf, sizeof(buf), &result);
 			if (len < 0) {
 				l2cap_send_disconn_req(chan, ECONNRESET);
 				goto done;
@@ -4201,7 +4207,7 @@ static inline int l2cap_config_rsp(struc
 			/* throw out any old stored conf requests */
 			result = L2CAP_CONF_SUCCESS;
 			len = l2cap_parse_conf_rsp(chan, rsp->data, len,
-						   req, &result);
+						   req, sizeof(req), &result);
 			if (len < 0) {
 				l2cap_send_disconn_req(chan, ECONNRESET);
 				goto done;
@@ -4782,7 +4788,7 @@ static void l2cap_do_create(struct l2cap
 			set_bit(CONF_REQ_SENT, &chan->conf_state);
 			l2cap_send_cmd(chan->conn, l2cap_get_ident(chan->conn),
 				       L2CAP_CONF_REQ,
-				       l2cap_build_conf_req(chan, buf), buf);
+				       l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
 			chan->num_conf_req++;
 		}
 	}
@@ -7361,7 +7367,7 @@ int l2cap_security_cfm(struct hci_conn *
 				set_bit(CONF_REQ_SENT, &chan->conf_state);
 				l2cap_send_cmd(conn, l2cap_get_ident(conn),
 					       L2CAP_CONF_REQ,
-					       l2cap_build_conf_req(chan, buf),
+					       l2cap_build_conf_req(chan, buf, sizeof(buf)),
 					       buf);
 				chan->num_conf_req++;
 			}