[PATCH net v3] net: nfc: nci: Fix parameter validation for packet data

[PATCH net v3] net: nfc: nci: Fix parameter validation for packet data

[Michael Thalmeier]

Since commit 9c328f54741b ("net: nfc: nci: Add parameter validation for
packet data") communication with nci nfc chips is not working any more.

The mentioned commit tries to fix access of uninitialized data, but
failed to understand that in some cases the data packet is of variable
length and can therefore not be compared to the maximum packet length
given by the sizeof(struct).

Fixes: 9c328f54741b ("net: nfc: nci: Add parameter validation for packet data")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Thalmeier <michael.thalmeier@hale.at>
---
v3:
- perform complete checks
- replace magic numbers with offsetofend and sizeof

v2:
- Reference correct commit hash

---
 net/nfc/nci/ntf.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c
index 418b84e2b260..0190332cf454 100644
--- a/net/nfc/nci/ntf.c
+++ b/net/nfc/nci/ntf.c
@@ -58,7 +58,7 @@ static int nci_core_conn_credits_ntf_packet(struct nci_dev *ndev,
 	struct nci_conn_info *conn_info;
 	int i;
 
-	if (skb->len < sizeof(struct nci_core_conn_credit_ntf))
+	if (skb->len < offsetofend(struct nci_core_conn_credit_ntf, num_entries))
 		return -EINVAL;
 
 	ntf = (struct nci_core_conn_credit_ntf *)skb->data;
@@ -68,6 +68,10 @@ static int nci_core_conn_credits_ntf_packet(struct nci_dev *ndev,
 	if (ntf->num_entries > NCI_MAX_NUM_CONN)
 		ntf->num_entries = NCI_MAX_NUM_CONN;
 
+	if (skb->len < offsetofend(struct nci_core_conn_credit_ntf, num_entries) +
+			ntf->num_entries * sizeof(struct conn_credit_entry))
+		return -EINVAL;
+
 	/* update the credits */
 	for (i = 0; i < ntf->num_entries; i++) {
 		ntf->conn_entries[i].conn_id =
@@ -364,7 +368,7 @@ static int nci_rf_discover_ntf_packet(struct nci_dev *ndev,
 	const __u8 *data;
 	bool add_target = true;
 
-	if (skb->len < sizeof(struct nci_rf_discover_ntf))
+	if (skb->len < offsetofend(struct nci_rf_discover_ntf, rf_tech_specific_params_len))
 		return -EINVAL;
 
 	data = skb->data;
@@ -380,6 +384,10 @@ static int nci_rf_discover_ntf_packet(struct nci_dev *ndev,
 	pr_debug("rf_tech_specific_params_len %d\n",
 		 ntf.rf_tech_specific_params_len);
 
+	if (skb->len < (data - skb->data) +
+                ntf.rf_tech_specific_params_len + sizeof(ntf.ntf_type))
+		return -EINVAL;
+
 	if (ntf.rf_tech_specific_params_len > 0) {
 		switch (ntf.rf_tech_and_mode) {
 		case NCI_NFC_A_PASSIVE_POLL_MODE:
@@ -596,7 +604,7 @@ static int nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
 	const __u8 *data;
 	int err = NCI_STATUS_OK;
 
-	if (skb->len < sizeof(struct nci_rf_intf_activated_ntf))
+	if (skb->len < offsetofend(struct nci_rf_intf_activated_ntf, rf_tech_specific_params_len))
 		return -EINVAL;
 
 	data = skb->data;
@@ -628,6 +636,9 @@ static int nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
 	if (ntf.rf_interface == NCI_RF_INTERFACE_NFCEE_DIRECT)
 		goto listen;
 
+	if (skb->len < (data - skb->data) + ntf.rf_tech_specific_params_len)
+		return -EINVAL;
+
 	if (ntf.rf_tech_specific_params_len > 0) {
 		switch (ntf.activation_rf_tech_and_mode) {
 		case NCI_NFC_A_PASSIVE_POLL_MODE:
@@ -668,6 +679,11 @@ static int nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
 		}
 	}
 
+	if (skb->len < (data - skb->data) + sizeof(ntf.data_exch_rf_tech_and_mode) +
+				sizeof(ntf.data_exch_tx_bit_rate) + sizeof (ntf.data_exch_rx_bit_rate) +
+				sizeof(ntf.activation_params_len))
+		return -EINVAL;
+
 	ntf.data_exch_rf_tech_and_mode = *data++;
 	ntf.data_exch_tx_bit_rate = *data++;
 	ntf.data_exch_rx_bit_rate = *data++;
@@ -679,6 +695,9 @@ static int nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
 	pr_debug("data_exch_rx_bit_rate 0x%x\n", ntf.data_exch_rx_bit_rate);
 	pr_debug("activation_params_len %d\n", ntf.activation_params_len);
 
+	if (skb->len < (data - skb->data) + ntf.activation_params_len)
+		return -EINVAL;
+
 	if (ntf.activation_params_len > 0) {
 		switch (ntf.rf_interface) {
 		case NCI_RF_INTERFACE_ISO_DEP:
-- 
2.52.0

Re: [PATCH net v3] net: nfc: nci: Fix parameter validation for packet data

[Vadim Fedorenko]

On 22/12/2025 14:31, Michael Thalmeier wrote:
> @@ -668,6 +679,11 @@ static int nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
>   		}
>   	}
>   
> +	if (skb->len < (data - skb->data) + sizeof(ntf.data_exch_rf_tech_and_mode) +
> +				sizeof(ntf.data_exch_tx_bit_rate) + sizeof (ntf.data_exch_rx_bit_rate) +

extra space between sizeof and the bracket

> +				sizeof(ntf.activation_params_len))
> +		return -EINVAL;
> +
>   	ntf.data_exch_rf_tech_and_mode = *data++;
>   	ntf.data_exch_tx_bit_rate = *data++;
>   	ntf.data_exch_rx_bit_rate = *data++;