netdev - [PATCH] nfc: st-nci: Fix potential buffer overflows in EVT

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Message-Id: <20211117171554.2731340-1-jordy@pwning.systems>
Date:   Wed, 17 Nov 2021 18:15:51 +0100
From:   Jordy Zomer <jordy@...ing.systems>
To:     linux-kernel@...r.kernel.org
Cc:     Jordy Zomer <jordy@...ing.systems>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        wengjianfeng <wengjianfeng@...ong.com>, netdev@...r.kernel.org
Subject: [PATCH] nfc: st-nci: 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.

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@...ing.systems>
---
 drivers/nfc/st-nci/se.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/nfc/st-nci/se.c b/drivers/nfc/st-nci/se.c
index 7764b1a4c3cf..0d22853925d8 100644
--- a/drivers/nfc/st-nci/se.c
+++ b/drivers/nfc/st-nci/se.c
@@ -335,6 +335,12 @@ static int st_nci_hci_connectivity_event_received(struct nci_dev *ndev,
 			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);
 
 		/* Check next byte is PARAMETERS tag (82) */
@@ -343,6 +349,15 @@ static int st_nci_hci_connectivity_event_received(struct nci_dev *ndev,
 			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