[PATCH v3] Bluetooth: L2CAP: Fix accepting multiple L2CAP_ECRED_CONN_REQ

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Currently the code attempts to accept requests regardless of the
command identifier which may cause multiple requests to be marked
as pending (FLAG_DEFER_SETUP) which can cause more than
L2CAP_ECRED_MAX_CID(5) to be allocated in l2cap_ecred_rsp_defer
causing an overflow.

The spec is quite clear that the same identifier shall not be used on
subsequent requests:

'Within each signaling channel a different Identifier shall be used
for each successive request or indication.'
https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-62/out/en/host/logical-link-control-and-adaptation-protocol-specification.html#UUID-32a25a06-4aa4-c6c7-77c5-dcfe3682355d

So this attempts to check if there are any channels pending with the
same identifier and rejects if any are found.

Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode")
Reported-by: Yiming Qian <yimingqian591@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 net/bluetooth/l2cap_core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 14131e427efd..f8f0f6f455c9 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -5072,6 +5072,13 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
 		goto response;
 	}
 
+	/* Check if there are no pending channels with the same ident */
+	__l2cap_chan_list_id(conn, cmd->ident, l2cap_ecred_list_defer, &result);
+	if (result) {
+		result = L2CAP_CR_LE_INVALID_PARAMS;
+		goto response;
+	}
+
 	cmd_len -= sizeof(*req);
 	num_scid = cmd_len / sizeof(u16);
 
-- 
2.53.0