Bluetooth: Prevent uninitialized data access in L2CAP configuration

When configuring an ERTM or streaming mode connection, remote devices
are expected to send an RFC option in a successful config response.  A
misbehaving remote device might not send an RFC option, and the L2CAP
code should not access uninitialized data in this case.

Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

1 files changed, 11 insertions, 1 deletions

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 5ea94a1eecf2..17b5b1cd9657 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -2152,7 +2152,7 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len, voi
         void *ptr = req->data;
         int type, olen;
         unsigned long val;
-        struct l2cap_conf_rfc rfc;
+        struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_BASIC };
 
         BT_DBG("chan %p, rsp %p, len %d, req %p", chan, rsp, len, data);
 
@@ -2271,6 +2271,16 @@ static void l2cap_conf_rfc_get(struct l2cap_chan *chan, void *rsp, int len)
                 }
         }
 
+        /* Use sane default values in case a misbehaving remote device
+         * did not send an RFC option.
+         */
+        rfc.mode = chan->mode;
+        rfc.retrans_timeout = cpu_to_le16(L2CAP_DEFAULT_RETRANS_TO);
+        rfc.monitor_timeout = cpu_to_le16(L2CAP_DEFAULT_MONITOR_TO);
+        rfc.max_pdu_size = cpu_to_le16(chan->imtu);
+
+        BT_ERR("Expected RFC option was not found, using defaults");
+
 done:
         switch (rfc.mode) {
         case L2CAP_MODE_ERTM: