NFC: protect nci_data_exchange transactions

Protect 'cb' and 'cb_context' arguments in nci_data_exchange.
In fact, this implements a queue with max length of 1 data
exchange transactions in parallel.

Signed-off-by: Ilan Elias <ilane@ti.com>
Acked-by: Lauro Ramos Venancio <lauro.venancio@openbossa.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 12 insertions, 2 deletions

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index 9f17e8ec0ab9..1e6b20f2bc99 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -453,6 +453,7 @@ static int nci_data_exchange(struct nfc_dev *nfc_dev, __u32 target_idx,
                                                 void *cb_context)
 {
         struct nci_dev *ndev = nfc_get_drvdata(nfc_dev);
+        int rc;
 
         nfc_dbg("entry, target_idx %d, len %d", target_idx, skb->len);
 
@@ -461,11 +462,18 @@ static int nci_data_exchange(struct nfc_dev *nfc_dev, __u32 target_idx,
                 return -EINVAL;
         }
 
+        if (test_and_set_bit(NCI_DATA_EXCHANGE, &ndev->flags))
+                return -EBUSY;
+
         /* store cb and context to be used on receiving data */
         ndev->data_exchange_cb = cb;
         ndev->data_exchange_cb_context = cb_context;
 
-        return nci_send_data(ndev, ndev->conn_id, skb);
+        rc = nci_send_data(ndev, ndev->conn_id, skb);
+        if (rc)
+                clear_bit(NCI_DATA_EXCHANGE, &ndev->flags);
+
+        return rc;
 }
 
 static struct nfc_ops nci_nfc_ops = {
diff --git a/net/nfc/nci/data.c b/net/nfc/nci/data.c
index 141790ada4aa..e5ed90fc1a9c 100644
--- a/net/nfc/nci/data.c
+++ b/net/nfc/nci/data.c
@@ -54,6 +54,8 @@ void nci_data_exchange_complete(struct nci_dev *ndev,
                 /* no waiting callback, free skb */
                 kfree_skb(skb);
         }
+
+        clear_bit(NCI_DATA_EXCHANGE, &ndev->flags);
 }
 
 /* ----------------- NCI TX Data ----------------- */
diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c
index 8dd75352ab6c..96633f5cda4f 100644
--- a/net/nfc/nci/ntf.c
+++ b/net/nfc/nci/ntf.c
@@ -215,7 +215,7 @@ static void nci_rf_deactivate_ntf_packet(struct nci_dev *ndev,
         }
 
         /* complete the data exchange transaction, if exists */
-        if (ndev->data_exchange_cb)
+        if (test_bit(NCI_DATA_EXCHANGE, &ndev->flags))
                 nci_data_exchange_complete(ndev, NULL, -EIO);
 }