[PATCH] Bluetooth: Add packet size checks for CAPI messages (CVE-2006-6106)

With malformed packets it might be possible to overwrite internal
CMTP and CAPI data structures. This patch adds additional length
checks to prevent these kinds of remote attacks.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

net/bluetooth/cmtp/capi.c

@@ -196,6 +196,9 @@ static void cmtp_recv_interopmsg(struct cmtp_session *session, struct sk_buff *s
 
 	switch (CAPIMSG_SUBCOMMAND(skb->data)) {
 	case CAPI_CONF:
+		if (skb->len < CAPI_MSG_BASELEN + 10)
+			break;
+
 		func = CAPIMSG_U16(skb->data, CAPI_MSG_BASELEN + 5);
 		info = CAPIMSG_U16(skb->data, CAPI_MSG_BASELEN + 8);
 
@@ -226,6 +229,9 @@ static void cmtp_recv_interopmsg(struct cmtp_session *session, struct sk_buff *s
 			break;
 
 		case CAPI_FUNCTION_GET_PROFILE:
+			if (skb->len < CAPI_MSG_BASELEN + 11 + sizeof(capi_profile))
+				break;
+
 			controller = CAPIMSG_U16(skb->data, CAPI_MSG_BASELEN + 11);
 			msgnum = CAPIMSG_MSGID(skb->data);
 
@@ -246,17 +252,26 @@ static void cmtp_recv_interopmsg(struct cmtp_session *session, struct sk_buff *s
 			break;
 
 		case CAPI_FUNCTION_GET_MANUFACTURER:
+			if (skb->len < CAPI_MSG_BASELEN + 15)
+				break;
+
 			controller = CAPIMSG_U32(skb->data, CAPI_MSG_BASELEN + 10);
 
 			if (!info && ctrl) {
-				strncpy(ctrl->manu,
-					skb->data + CAPI_MSG_BASELEN + 15,
+				int len = min_t(uint, CAPI_MANUFACTURER_LEN,
 						skb->data[CAPI_MSG_BASELEN + 14]);
+
+				memset(ctrl->manu, 0, CAPI_MANUFACTURER_LEN);
+				strncpy(ctrl->manu,
+					skb->data + CAPI_MSG_BASELEN + 15, len);
 			}
 
 			break;
 
 		case CAPI_FUNCTION_GET_VERSION:
+			if (skb->len < CAPI_MSG_BASELEN + 32)
+				break;
+
 			controller = CAPIMSG_U32(skb->data, CAPI_MSG_BASELEN + 12);
 
 			if (!info && ctrl) {
@@ -269,13 +284,18 @@ static void cmtp_recv_interopmsg(struct cmtp_session *session, struct sk_buff *s
 			break;
 
 		case CAPI_FUNCTION_GET_SERIAL_NUMBER:
+			if (skb->len < CAPI_MSG_BASELEN + 17)
+				break;
+
 			controller = CAPIMSG_U32(skb->data, CAPI_MSG_BASELEN + 12);
 
 			if (!info && ctrl) {
+				int len = min_t(uint, CAPI_SERIAL_LEN,
+						skb->data[CAPI_MSG_BASELEN + 16]);
+
 				memset(ctrl->serial, 0, CAPI_SERIAL_LEN);
 				strncpy(ctrl->serial,
-					skb->data + CAPI_MSG_BASELEN + 17,
-					skb->data[CAPI_MSG_BASELEN + 16]);
+					skb->data + CAPI_MSG_BASELEN + 17, len);
 			}
 
 			break;
@@ -284,14 +304,18 @@ static void cmtp_recv_interopmsg(struct cmtp_session *session, struct sk_buff *s
 		break;
 
 	case CAPI_IND:
+		if (skb->len < CAPI_MSG_BASELEN + 6)
+			break;
+
 		func = CAPIMSG_U16(skb->data, CAPI_MSG_BASELEN + 3);
 
 		if (func == CAPI_FUNCTION_LOOPBACK) {
+			int len = min_t(uint, skb->len - CAPI_MSG_BASELEN - 6,
+						skb->data[CAPI_MSG_BASELEN + 5]);
 			appl = CAPIMSG_APPID(skb->data);
 			msgnum = CAPIMSG_MSGID(skb->data);
 			cmtp_send_interopmsg(session, CAPI_RESP, appl, msgnum, func,
-						skb->data + CAPI_MSG_BASELEN + 6,
-						skb->data[CAPI_MSG_BASELEN + 5]);
+						skb->data + CAPI_MSG_BASELEN + 6, len);
 		}
 
 		break;
@@ -309,6 +333,9 @@ void cmtp_recv_capimsg(struct cmtp_session *session, struct sk_buff *skb)
 
 	BT_DBG("session %p skb %p len %d", session, skb, skb->len);
 
+	if (skb->len < CAPI_MSG_BASELEN)
+		return;
+
 	if (CAPIMSG_COMMAND(skb->data) == CAPI_INTEROPERABILITY) {
 		cmtp_recv_interopmsg(session, skb);
 		return;