nfc: st21nfca: Fix potential buffer overflows in EVT_TRANSACTION

It appears that there are some buffer overflows in EVT_TRANSACTION.
This happens because the length parameters that are passed to memcpy
come directly from skb->data and are not guarded in any way.

Signed-off-by: Jordy Zomer <jordy@pwning.systems>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/nfc/st21nfca/se.c b/drivers/nfc/st21nfca/se.c
index a43fc41..c922f10 100644 (file)
--- a/drivers/nfc/st21nfca/se.c
+++ b/drivers/nfc/st21nfca/se.c
@@ -316,6 +316,11 @@ int st21nfca_connectivity_event_received(struct nfc_hci_dev *hdev, u8 host,
                        return -ENOMEM;
 
                transaction->aid_len = skb->data[1];
+
+               /* Checking if the length of the AID is valid */
+               if (transaction->aid_len > sizeof(transaction->aid))
+                       return -EINVAL;
+
                memcpy(transaction->aid, &skb->data[2],
                       transaction->aid_len);
 
@@ -325,6 +330,11 @@ int st21nfca_connectivity_event_received(struct nfc_hci_dev *hdev, u8 host,
                        return -EPROTO;
 
                transaction->params_len = skb->data[transaction->aid_len + 3];
+
+               /* Total size is allocated (skb->len - 2) minus fixed array members */
+               if (transaction->params_len > ((skb->len - 2) - sizeof(struct nfc_evt_transaction)))
+                       return -EINVAL;
+
                memcpy(transaction->params, skb->data +
                       transaction->aid_len + 4, transaction->params_len);