[RFC][PATCH 2/4] NFC: st21nfca: Fix memory OOB and leak issues in connectivity events handler

[Amit Pundir]

From: Suren Baghdasaryan <sur...@google.com>

Overflow on memcpy is possible in kernel driver for st21nfca's
NFC HCI layer when handling connectivity events if aid_len or
params_len are bigger than the buffer size.
Memory leak is possible when parameter tag is invalid.

Signed-off-by: Suren Baghdasaryan <sur...@google.com>
Signed-off-by: Amit Pundir <amit.pun...@linaro.org>
---
 drivers/nfc/st21nfca/se.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/nfc/st21nfca/se.c b/drivers/nfc/st21nfca/se.c
index 4bed9e842db3..acdce231e227 100644
--- a/drivers/nfc/st21nfca/se.c
+++ b/drivers/nfc/st21nfca/se.c
@@ -322,23 +322,33 @@ int st21nfca_connectivity_event_received(struct 
nfc_hci_dev *hdev, u8 host,
                 * AID          81      5 to 16
                 * PARAMETERS   82      0 to 255
                 */
-               if (skb->len < NFC_MIN_AID_LENGTH + 2 &&
+               if (skb->len < NFC_MIN_AID_LENGTH + 2 ||
                    skb->data[0] != NFC_EVT_TRANSACTION_AID_TAG)
                        return -EPROTO;
 
+               /*
+                * Buffer should have enough space for at least
+                * two tag fields + two length fields + aid_len (skb->data[1])
+                */
+               if (skb->len < skb->data[1] + 4)
+                       return -EPROTO;
+
                transaction = (struct nfc_evt_transaction *)devm_kzalloc(dev,
                                                   skb->len - 2, GFP_KERNEL);
 
                transaction->aid_len = skb->data[1];
                memcpy(transaction->aid, &skb->data[2],
                       transaction->aid_len);
+               transaction->params_len = skb->data[transaction->aid_len + 3];
 
-               /* Check next byte is PARAMETERS tag (82) */
+               /* Check next byte is PARAMETERS tag (82) and the length field 
*/
                if (skb->data[transaction->aid_len + 2] !=
-                   NFC_EVT_TRANSACTION_PARAMS_TAG)
+                   NFC_EVT_TRANSACTION_PARAMS_TAG ||
+                   skb->len < transaction->aid_len + transaction->params_len + 
4) {
+                       devm_kfree(dev, transaction);
                        return -EPROTO;
+               }
 
-               transaction->params_len = skb->data[transaction->aid_len + 3];
                memcpy(transaction->params, skb->data +
                       transaction->aid_len + 4, transaction->params_len);
 
-- 
2.7.4