CVE-2017-1000251 (published 2017-09-12T17:29Z)

The native Bluetooth stack in the Linux Kernel (BlueZ), starting at the Linux kernel version 2.6.32 and up to and including 4.13.1, are vulnerable to a stack overflow vulnerability in the processing of L2CAP configuration responses resulting in Remote code execution in kernel space.

Severity: HIGH
CVSS v2 base score: 7.7 (AV:A/AC:L/Au:S/C:C/I:C/A:C)
CVSS v3 base score: 8.0, HIGH (CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-787
cwe_name: Out-of-bounds Write
description: The product writes data past the end, or before the beginning, of the intended buffer.
extended_description: 
            
            
             
			 
         
         

Fix information:
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: Gustavo F. Padovan
author_date: 2009-07-04 15:06:24-03:00
msg: Bluetooth: Add configuration support for ERTM and Streaming mode

Add support to config_req and config_rsp to configure ERTM and Streaming
mode. If the remote device specifies ERTM or Streaming mode, then the
same mode is proposed. Otherwise ERTM or Basic mode is used. And in case
of a state 2 device, the remote device should propose the same mode. If
not, then the channel gets disconnected.

Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: l2cap.h
change_type: ModificationType.MODIFY
diff: @@ -27,8 +27,9 @@
 
 /* L2CAP defaults */
 #define L2CAP_DEFAULT_MTU		672
+#define L2CAP_DEFAULT_MIN_MTU		48
 #define L2CAP_DEFAULT_FLUSH_TO		0xffff
-#define L2CAP_DEFAULT_RX_WINDOW		1
+#define L2CAP_DEFAULT_TX_WINDOW		1
 #define L2CAP_DEFAULT_MAX_RECEIVE	1
 #define L2CAP_DEFAULT_RETRANS_TO	300    /* 300 milliseconds */
 #define L2CAP_DEFAULT_MONITOR_TO	1000   /* 1 second */
@@ -272,6 +273,9 @@ struct l2cap_pinfo {
 	__u16		omtu;
 	__u16		flush_to;
 	__u8		mode;
+	__u8		num_conf_req;
+	__u8		num_conf_rsp;
+
 	__u8		fcs;
 	__u8		sec_level;
 	__u8		role_switch;
@@ -280,10 +284,15 @@ struct l2cap_pinfo {
 	__u8		conf_req[64];
 	__u8		conf_len;
 	__u8		conf_state;
-	__u8		conf_retry;
 
 	__u8		ident;
 
+	__u8		remote_tx_win;
+	__u8		remote_max_tx;
+	__u16		retrans_timeout;
+	__u16		monitor_timeout;
+	__u16		max_pdu_size;
+
 	__le16		sport;
 
 	struct l2cap_conn	*conn;
@@ -291,12 +300,17 @@ struct l2cap_pinfo {
 	struct sock		*prev_c;
 };
 
-#define L2CAP_CONF_REQ_SENT	0x01
-#define L2CAP_CONF_INPUT_DONE	0x02
-#define L2CAP_CONF_OUTPUT_DONE	0x04
-#define L2CAP_CONF_CONNECT_PEND	0x80
+#define L2CAP_CONF_REQ_SENT       0x01
+#define L2CAP_CONF_INPUT_DONE     0x02
+#define L2CAP_CONF_OUTPUT_DONE    0x04
+#define L2CAP_CONF_MTU_DONE       0x08
+#define L2CAP_CONF_MODE_DONE      0x10
+#define L2CAP_CONF_CONNECT_PEND   0x20
+#define L2CAP_CONF_STATE2_DEVICE  0x80
+
+#define L2CAP_CONF_MAX_CONF_REQ 2
+#define L2CAP_CONF_MAX_CONF_RSP 2
 
-#define L2CAP_CONF_MAX_RETRIES	2
 
 void l2cap_load(void);
 

programming_language: C
filename: l2cap.c
change_type: ModificationType.MODIFY
diff: @@ -966,6 +966,7 @@ static int l2cap_sock_connect(struct socket *sock, struct sockaddr *addr, int al
 	case L2CAP_MODE_BASIC:
 		break;
 	case L2CAP_MODE_ERTM:
+	case L2CAP_MODE_STREAMING:
 		if (enable_ertm)
 			break;
 		/* fall through */
@@ -1029,6 +1030,7 @@ static int l2cap_sock_listen(struct socket *sock, int backlog)
 	case L2CAP_MODE_BASIC:
 		break;
 	case L2CAP_MODE_ERTM:
+	case L2CAP_MODE_STREAMING:
 		if (enable_ertm)
 			break;
 		/* fall through */
@@ -1739,15 +1741,65 @@ static void l2cap_add_conf_opt(void **ptr, u8 type, u8 len, unsigned long val)
 	*ptr += L2CAP_CONF_OPT_SIZE + len;
 }
 
+static int l2cap_mode_supported(__u8 mode, __u32 feat_mask)
+{
+	u32 local_feat_mask = l2cap_feat_mask;
+	if (enable_ertm)
+		local_feat_mask |= L2CAP_FEAT_ERTM;
+
+	switch (mode) {
+	case L2CAP_MODE_ERTM:
+		return L2CAP_FEAT_ERTM & feat_mask & local_feat_mask;
+	case L2CAP_MODE_STREAMING:
+		return L2CAP_FEAT_STREAMING & feat_mask & local_feat_mask;
+	default:
+		return 0x00;
+	}
+}
+
+static inline __u8 l2cap_select_mode(__u8 mode, __u16 remote_feat_mask)
+{
+	switch (mode) {
+	case L2CAP_MODE_STREAMING:
+	case L2CAP_MODE_ERTM:
+		if (l2cap_mode_supported(mode, remote_feat_mask))
+			return mode;
+		/* fall through */
+	default:
+		return L2CAP_MODE_BASIC;
+	}
+}
+
 static int l2cap_build_conf_req(struct sock *sk, void *data)
 {
 	struct l2cap_pinfo *pi = l2cap_pi(sk);
 	struct l2cap_conf_req *req = data;
-	struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_BASIC };
+	struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_ERTM };
 	void *ptr = req->data;
 
 	BT_DBG("sk %p", sk);
 
+	if (pi->num_conf_req || pi->num_conf_rsp)
+		goto done;
+
+	switch (pi->mode) {
+	case L2CAP_MODE_STREAMING:
+	case L2CAP_MODE_ERTM:
+		pi->conf_state |= L2CAP_CONF_STATE2_DEVICE;
+		if (!l2cap_mode_supported(pi->mode, pi->conn->feat_mask)) {
+			struct l2cap_disconn_req req;
+			req.dcid = cpu_to_le16(pi->dcid);
+			req.scid = cpu_to_le16(pi->scid);
+			l2cap_send_cmd(pi->conn, l2cap_get_ident(pi->conn),
+					L2CAP_DISCONN_REQ, sizeof(req), &req);
+		}
+		break;
+	default:
+		pi->mode = l2cap_select_mode(rfc.mode, pi->conn->feat_mask);
+		break;
+	}
+
+done:
 	switch (pi->mode) {
 	case L2CAP_MODE_BASIC:
 		if (pi->imtu != L2CAP_DEFAULT_MTU)
@@ -1756,10 +1808,22 @@ static int l2cap_build_conf_req(struct sock *sk, void *data)
 
 	case L2CAP_MODE_ERTM:
 		rfc.mode            = L2CAP_MODE_ERTM;
-		rfc.txwin_size      = L2CAP_DEFAULT_RX_WINDOW;
+		rfc.txwin_size      = L2CAP_DEFAULT_TX_WINDOW;
 		rfc.max_transmit    = L2CAP_DEFAULT_MAX_RECEIVE;
-		rfc.retrans_timeout = cpu_to_le16(L2CAP_DEFAULT_RETRANS_TO);
-		rfc.monitor_timeout = cpu_to_le16(L2CAP_DEFAULT_MONITOR_TO);
+		rfc.retrans_timeout = 0;
+		rfc.monitor_timeout = 0;
+		rfc.max_pdu_size    = cpu_to_le16(L2CAP_DEFAULT_MAX_RX_APDU);
+
+		l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
+					sizeof(rfc), (unsigned long) &rfc);
+		break;
+
+	case L2CAP_MODE_STREAMING:
+		rfc.mode            = L2CAP_MODE_STREAMING;
+		rfc.txwin_size      = 0;
+		rfc.max_transmit    = 0;
+		rfc.retrans_timeout = 0;
+		rfc.monitor_timeout = 0;
 		rfc.max_pdu_size    = cpu_to_le16(L2CAP_DEFAULT_MAX_RX_APDU);
 
 		l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
@@ -1825,30 +1889,83 @@ static int l2cap_parse_conf_req(struct sock *sk, void *data)
 		}
 	}
 
+	if (pi->num_conf_rsp || pi->num_conf_req)
+		goto done;
+
+	switch (pi->mode) {
+	case L2CAP_MODE_STREAMING:
+	case L2CAP_MODE_ERTM:
+		pi->conf_state |= L2CAP_CONF_STATE2_DEVICE;
+		if (!l2cap_mode_supported(pi->mode, pi->conn->feat_mask))
+			return -ECONNREFUSED;
+		break;
+	default:
+		pi->mode = l2cap_select_mode(rfc.mode, pi->conn->feat_mask);
+		break;
+	}
+
+done:
+	if (pi->mode != rfc.mode) {
+		result = L2CAP_CONF_UNACCEPT;
+		rfc.mode = pi->mode;
+
+		if (pi->num_conf_rsp == 1)
+			return -ECONNREFUSED;
+
+		l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
+					sizeof(rfc), (unsigned long) &rfc);
+	}
+
+
 	if (result == L2CAP_CONF_SUCCESS) {
 		/* Configure output options and let the other side know
 		 * which ones we don't like. */
 
-		if (rfc.mode == L2CAP_MODE_BASIC) {
-			if (mtu < pi->omtu)
-				result = L2CAP_CONF_UNACCEPT;
-			else {
-				pi->omtu = mtu;
-				pi->conf_state |= L2CAP_CONF_OUTPUT_DONE;
-			}
+		if (mtu < L2CAP_DEFAULT_MIN_MTU)
+			result = L2CAP_CONF_UNACCEPT;
+		else {
+			pi->omtu = mtu;
+			pi->conf_state |= L2CAP_CONF_MTU_DONE;
+		}
+		l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, pi->omtu);
 
-			l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, pi->omtu);
-		} else {
+		switch (rfc.mode) {
+		case L2CAP_MODE_BASIC:
+			pi->fcs = L2CAP_FCS_NONE;
+			pi->conf_state |= L2CAP_CONF_MODE_DONE;
+			break;
+
+		case L2CAP_MODE_ERTM:
+			pi->remote_tx_win = rfc.txwin_size;
+			pi->remote_max_tx = rfc.max_transmit;
+			pi->max_pdu_size = rfc.max_pdu_size;
+
+			rfc.retrans_timeout = L2CAP_DEFAULT_RETRANS_TO;
+			rfc.monitor_timeout = L2CAP_DEFAULT_MONITOR_TO;
+
+			pi->conf_state |= L2CAP_CONF_MODE_DONE;
+			break;
+
+		case L2CAP_MODE_STREAMING:
+			pi->remote_tx_win = rfc.txwin_size;
+			pi->max_pdu_size = rfc.max_pdu_size;
+
+			pi->conf_state |= L2CAP_CONF_MODE_DONE;
+			break;
+
+		default:
 			result = L2CAP_CONF_UNACCEPT;
 
 			memset(&rfc, 0, sizeof(rfc));
-			rfc.mode = L2CAP_MODE_BASIC;
+			rfc.mode = pi->mode;
+		}
 
-			l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
+		l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
 					sizeof(rfc), (unsigned long) &rfc);
-		}
-	}
 
+		if (result == L2CAP_CONF_SUCCESS)
+			pi->conf_state |= L2CAP_CONF_OUTPUT_DONE;
+	}
 	rsp->scid   = cpu_to_le16(pi->dcid);
 	rsp->result = cpu_to_le16(result);
 	rsp->flags  = cpu_to_le16(0x0000);
@@ -1856,6 +1973,73 @@ static int l2cap_parse_conf_req(struct sock *sk, void *data)
 	return ptr - data;
 }
 
+static int l2cap_parse_conf_rsp(struct sock *sk, void *rsp, int len, void *data, u16 *result)
+{
+	struct l2cap_pinfo *pi = l2cap_pi(sk);
+	struct l2cap_conf_req *req = data;
+	void *ptr = req->data;
+	int type, olen;
+	unsigned long val;
+	struct l2cap_conf_rfc rfc;
+
+	BT_DBG("sk %p, rsp %p, len %d, req %p", sk, rsp, len, data);
+
+	while (len >= L2CAP_CONF_OPT_SIZE) {
+		len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val);
+
+		switch (type) {
+		case L2CAP_CONF_MTU:
+			if (val < L2CAP_DEFAULT_MIN_MTU) {
+				*result = L2CAP_CONF_UNACCEPT;
+				pi->omtu = L2CAP_DEFAULT_MIN_MTU;
+			} else
+				pi->omtu = val;
+			l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, pi->omtu);
+			break;
+
+		case L2CAP_CONF_FLUSH_TO:
+			pi->flush_to = val;
+			l2cap_add_conf_opt(&ptr, L2CAP_CONF_FLUSH_TO,
+							2, pi->flush_to);
+			break;
+
+		case L2CAP_CONF_RFC:
+			if (olen == sizeof(rfc))
+				memcpy(&rfc, (void *)val, olen);
+
+			if ((pi->conf_state & L2CAP_CONF_STATE2_DEVICE) &&
+							rfc.mode != pi->mode)
+				return -ECONNREFUSED;
+
+			pi->mode = rfc.mode;
+			pi->fcs = 0;
+
+			l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
+					sizeof(rfc), (unsigned long) &rfc);
+			break;
+		}
+	}
+
+	if (*result == L2CAP_CONF_SUCCESS) {
+		switch (rfc.mode) {
+		case L2CAP_MODE_ERTM:
+			pi->remote_tx_win   = rfc.txwin_size;
+			pi->retrans_timeout = rfc.retrans_timeout;
+			pi->monitor_timeout = rfc.monitor_timeout;
+			pi->max_pdu_size    = le16_to_cpu(rfc.max_pdu_size);
+			break;
+		case L2CAP_MODE_STREAMING:
+			pi->max_pdu_size    = le16_to_cpu(rfc.max_pdu_size);
+			break;
+		}
+	}
+
+	req->dcid   = cpu_to_le16(pi->dcid);
+	req->flags  = cpu_to_le16(0x0000);
+
+	return ptr - data;
+}
+
 static int l2cap_build_conf_rsp(struct sock *sk, void *data, u16 result, u16 flags)
 {
 	struct l2cap_conf_rsp *rsp = data;
@@ -2042,6 +2226,7 @@ static inline int l2cap_connect_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hd
 
 		l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
 					l2cap_build_conf_req(sk, req), req);
+		l2cap_pi(sk)->num_conf_req++;
 		break;
 
 	case L2CAP_CR_PEND:
@@ -2100,10 +2285,17 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 
 	/* Complete config. */
 	len = l2cap_parse_conf_req(sk, rsp);
-	if (len < 0)
+	if (len < 0) {
+		struct l2cap_disconn_req req;
+		req.dcid = cpu_to_le16(l2cap_pi(sk)->dcid);
+		req.scid = cpu_to_le16(l2cap_pi(sk)->scid);
+		l2cap_send_cmd(conn, l2cap_get_ident(conn),
+					L2CAP_DISCONN_REQ, sizeof(req), &req);
 		goto unlock;
+	}
 
 	l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP, len, rsp);
+	l2cap_pi(sk)->num_conf_rsp++;
 
 	/* Reset config buffer. */
 	l2cap_pi(sk)->conf_len = 0;
@@ -2121,6 +2313,7 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 		u8 buf[64];
 		l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
 					l2cap_build_conf_req(sk, buf), buf);
+		l2cap_pi(sk)->num_conf_req++;
 	}
 
 unlock:
@@ -2150,16 +2343,29 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 		break;
 
 	case L2CAP_CONF_UNACCEPT:
-		if (++l2cap_pi(sk)->conf_retry < L2CAP_CONF_MAX_RETRIES) {
-			char req[128];
-			/* It does not make sense to adjust L2CAP parameters
-			 * that are currently defined in the spec. We simply
-			 * resend config request that we sent earlier. It is
-			 * stupid, but it helps qualification testing which
-			 * expects at least some response from us. */
-			l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
-						l2cap_build_conf_req(sk, req), req);
-			goto done;
+		if (l2cap_pi(sk)->num_conf_rsp <= L2CAP_CONF_MAX_CONF_RSP) {
+			int len = cmd->len - sizeof(*rsp);
+			char req[64];
+
+			/* throw out any old stored conf requests */
+			result = L2CAP_CONF_SUCCESS;
+			len = l2cap_parse_conf_rsp(sk, rsp->data,
+							len, req, &result);
+			if (len < 0) {
+				struct l2cap_disconn_req req;
+				req.dcid = cpu_to_le16(l2cap_pi(sk)->dcid);
+				req.scid = cpu_to_le16(l2cap_pi(sk)->scid);
+				l2cap_send_cmd(conn, l2cap_get_ident(conn),
+					L2CAP_DISCONN_REQ, sizeof(req), &req);
+				goto done;
+			}
+
+			l2cap_send_cmd(conn, l2cap_get_ident(conn),
+						L2CAP_CONF_REQ, len, req);
+			l2cap_pi(sk)->num_conf_req++;
+			if (result != L2CAP_CONF_SUCCESS)
+				goto done;
+			break;
 		}
 
 	default:

programming_language: C