[Bluetooth] Add packet size checks for CAPI messages

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>

diff --git a/net/bluetooth/cmtp/capi.c b/net/bluetooth/cmtp/capi.c
index be04e9fb11f604639f92e447451098902a9977d6..ab166b48ce8dc02c8288b44d21d4d9c5ce7b2d22 100644 (file)
--- a/net/bluetooth/cmtp/capi.c
+++ b/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) {
+                               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,
-                                       skb->data[CAPI_MSG_BASELEN + 14]);
+                                       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;