[PATCHv2] Bluetooth: Prevent uninitialized data access in L2CAP configuration

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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@xxxxxxxxxxxxxx>
---
 net/bluetooth/l2cap_core.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 5ea94a1..45dd423 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 +2271,15 @@ 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.
+	 */
+	BT_ERR("Expected RFC option was not found, using defaults");
+	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);
+
 done:
 	switch (rfc.mode) {
 	case L2CAP_MODE_ERTM:
-- 
1.7.8

--
Mat Martineau
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum
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