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Subject[PATCH] nfc: st21nfca: Fix potential buffer overflows in EVT_TRANSACTION
Date
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.

It would be nice if someone can review and test this patch because
I don't own the hardware :)

Signed-off-by: Jordy Zomer <jordy@pwning.systems>
---
drivers/nfc/st21nfca/se.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/drivers/nfc/st21nfca/se.c b/drivers/nfc/st21nfca/se.c
index a43fc4117fa5..e3483aca3280 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 +330,14 @@ int st21nfca_connectivity_event_received(struct nfc_hci_dev *hdev, u8 host,
return -EPROTO;

transaction->params_len = skb->data[transaction->aid_len + 3];
+
+ // check if the length of the parameters is valid
+ // we can't use sizeof(transaction->params) because it's
+ // a flexible array member so we have to check if params_len
+ // is bigger than the space allocated for the array
+ 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
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