Bluetooth: MGMT: validate mesh send advertising payload length

mesh_send() currently bounds MGMT_OP_MESH_SEND by total command
length, but it never verifies that the bytes supplied for the
flexible adv_data[] array actually match the embedded adv_data_len
field. MGMT_MESH_SEND_SIZE only covers the fixed header, so a
truncated command can still pass the existing 20..50 byte range
check and later drive the async mesh send path past the end of the
queued command buffer.

Keep rejecting zero-length and oversized advertising payloads, but
validate adv_data_len explicitly and require the command length to
exactly match the flexible array size before queueing the request.

Fixes: b338d91 ("Bluetooth: Implement support for Mesh")
Reported-by: Keenan Dong <keenanat2000@gmail.com>
Signed-off-by: Keenan Dong <keenanat2000@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Author: Niebelungen-D

net/bluetooth/mgmt.c

@@ -2478,19 +2478,27 @@ static int mesh_send(struct sock *sk, struct hci_dev *hdev, void *data, u16 len)
 	struct mgmt_mesh_tx *mesh_tx;
 	struct mgmt_cp_mesh_send *send = data;
 	struct mgmt_rp_mesh_read_features rp;
+	u16 expected_len;
 	bool sending;
 	int err = 0;
 
 	if (!lmp_le_capable(hdev) ||
 	    !hci_dev_test_flag(hdev, HCI_MESH_EXPERIMENTAL))
 		return mgmt_cmd_status(sk, hdev->id, MGMT_OP_MESH_SEND,
 				       MGMT_STATUS_NOT_SUPPORTED);
-	if (!hci_dev_test_flag(hdev, HCI_LE_ENABLED) ||
-	    len <= MGMT_MESH_SEND_SIZE ||
-	    len > (MGMT_MESH_SEND_SIZE + 31))
+	if (!hci_dev_test_flag(hdev, HCI_LE_ENABLED))
+		return mgmt_cmd_status(sk, hdev->id, MGMT_OP_MESH_SEND,
+				       MGMT_STATUS_REJECTED);
+
+	if (!send->adv_data_len || send->adv_data_len > 31)
 		return mgmt_cmd_status(sk, hdev->id, MGMT_OP_MESH_SEND,
 				       MGMT_STATUS_REJECTED);
 
+	expected_len = struct_size(send, adv_data, send->adv_data_len);
+	if (expected_len != len)
+		return mgmt_cmd_status(sk, hdev->id, MGMT_OP_MESH_SEND,
+				       MGMT_STATUS_INVALID_PARAMS);
+
 	hci_dev_lock(hdev);
 
 	memset(&rp, 0, sizeof(rp));