[PATCH v3] nfc: st21nfca: Fix potential buffer overflows in EVT_TRANSACTION

From: Jordy Zomer
Date: Tue Jan 11 2022 - 11:45:04 EST


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>
---
drivers/nfc/st21nfca/se.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/nfc/st21nfca/se.c b/drivers/nfc/st21nfca/se.c
index a43fc4117fa5..c922f10d0d7b 100644
--- 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);

--
2.27.0