[PATCH net v4] net: nfc: nci: Add parameter validation for packet data

[PATCH net v4] net: nfc: nci: Add parameter validation for packet data

[Deepak Sharma]

Syzbot reported an uninitialized value bug in nci_init_req, which was 
introduced by commit 5aca7966d2a7 ("Merge tag 
'perf-tools-fixes-for-v6.17-2025-09-16' of 
git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools").

This bug arises due to very limited and poor input validation
that was done at nic_valid_size(). This validation only
validates the skb->len (directly reflects size provided at the
userspace interface) with the length provided in the buffer
itself (interpreted as NCI_HEADER). This leads to the processing
of memory content at the address assuming the correct layout
per what opcode requires there. This leads to the accesses to
buffer of `skb_buff->data` which is not assigned anything yet.

Following the same silent drop of packets of invalid sizes at
`nic_valid_size()`, add validation of the data in the respective
handlers and return error values in case of failure. Release
the skb if error values are returned from handlers in 
`nci_nft_packet` and effectively do a silent drop

Possible TODO: because we silently drop the packets, the
call to `nci_request` will be waiting for completion of request
and will face timeouts. These timeouts can get excessively logged
in the dmesg. A proper handling of them may require to export
`nci_request_cancel` (or propagate error handling from the
nft packets handlers).

Reported-by: syzbot+740e04c2a93467a0f8c8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=740e04c2a93467a0f8c8
Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation")
Tested-by: syzbot+740e04c2a93467a0f8c8@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Deepak Sharma <deepak.sharma.472935@gmail.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
---
v4:
 - Remove changes unrelated to the fix

v3:
 - Move the checks inside the packet data handlers
 - Improvements to the commit message

v2:
 - Fix the release of skb in case of the early return

v1:
 - Add checks in `nci_ntf_packet` on the skb->len and do early return
   on failure

 net/nfc/nci/ntf.c | 139 +++++++++++++++++++++++++++++++++-------------
 1 file changed, 101 insertions(+), 38 deletions(-)

diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c
index a818eff27e6b..c0edf8242e22 100644
--- a/net/nfc/nci/ntf.c
+++ b/net/nfc/nci/ntf.c
@@ -27,11 +27,16 @@
 
 /* Handle NCI Notification packets */
 
-static void nci_core_reset_ntf_packet(struct nci_dev *ndev,
-				      const struct sk_buff *skb)
+static int nci_core_reset_ntf_packet(struct nci_dev *ndev,
+				     const struct sk_buff *skb)
 {
 	/* Handle NCI 2.x core reset notification */
-	const struct nci_core_reset_ntf *ntf = (void *)skb->data;
+	const struct nci_core_reset_ntf *ntf;
+
+	if (skb->len < sizeof(struct nci_core_reset_ntf))
+		return -EINVAL;
+
+	ntf = (struct nci_core_reset_ntf *)skb->data;
 
 	ndev->nci_ver = ntf->nci_ver;
 	pr_debug("nci_ver 0x%x, config_status 0x%x\n",
@@ -42,15 +47,22 @@ static void nci_core_reset_ntf_packet(struct nci_dev *ndev,
 		__le32_to_cpu(ntf->manufact_specific_info);
 
 	nci_req_complete(ndev, NCI_STATUS_OK);
+
+	return 0;
 }
 
-static void nci_core_conn_credits_ntf_packet(struct nci_dev *ndev,
-					     struct sk_buff *skb)
+static int nci_core_conn_credits_ntf_packet(struct nci_dev *ndev,
+					    struct sk_buff *skb)
 {
-	struct nci_core_conn_credit_ntf *ntf = (void *) skb->data;
+	struct nci_core_conn_credit_ntf *ntf;
 	struct nci_conn_info *conn_info;
 	int i;
 
+	if (skb->len < sizeof(struct nci_core_conn_credit_ntf))
+		return -EINVAL;
+
+	ntf = (struct nci_core_conn_credit_ntf *)skb->data;
+
 	pr_debug("num_entries %d\n", ntf->num_entries);
 
 	if (ntf->num_entries > NCI_MAX_NUM_CONN)
@@ -68,7 +80,7 @@ static void nci_core_conn_credits_ntf_packet(struct nci_dev *ndev,
 		conn_info = nci_get_conn_info_by_conn_id(ndev,
 							 ntf->conn_entries[i].conn_id);
 		if (!conn_info)
-			return;
+			return 0;
 
 		atomic_add(ntf->conn_entries[i].credits,
 			   &conn_info->credits_cnt);
@@ -77,12 +89,19 @@ static void nci_core_conn_credits_ntf_packet(struct nci_dev *ndev,
 	/* trigger the next tx */
 	if (!skb_queue_empty(&ndev->tx_q))
 		queue_work(ndev->tx_wq, &ndev->tx_work);
+
+	return 0;
 }
 
-static void nci_core_generic_error_ntf_packet(struct nci_dev *ndev,
-					      const struct sk_buff *skb)
+static int nci_core_generic_error_ntf_packet(struct nci_dev *ndev,
+					     const struct sk_buff *skb)
 {
-	__u8 status = skb->data[0];
+	__u8 status;
+
+	if (skb->len < 1)
+		return -EINVAL;
+
+	status = skb->data[0];
 
 	pr_debug("status 0x%x\n", status);
 
@@ -91,12 +110,19 @@ static void nci_core_generic_error_ntf_packet(struct nci_dev *ndev,
 		   (the state remains the same) */
 		nci_req_complete(ndev, status);
 	}
+
+	return 0;
 }
 
-static void nci_core_conn_intf_error_ntf_packet(struct nci_dev *ndev,
-						struct sk_buff *skb)
+static int nci_core_conn_intf_error_ntf_packet(struct nci_dev *ndev,
+					       struct sk_buff *skb)
 {
-	struct nci_core_intf_error_ntf *ntf = (void *) skb->data;
+	struct nci_core_intf_error_ntf *ntf;
+
+	if (skb->len < sizeof(struct nci_core_intf_error_ntf))
+		return -EINVAL;
+
+	ntf = (struct nci_core_intf_error_ntf *)skb->data;
 
 	ntf->conn_id = nci_conn_id(&ntf->conn_id);
 
@@ -105,6 +131,8 @@ static void nci_core_conn_intf_error_ntf_packet(struct nci_dev *ndev,
 	/* complete the data exchange transaction, if exists */
 	if (test_bit(NCI_DATA_EXCHANGE, &ndev->flags))
 		nci_data_exchange_complete(ndev, NULL, ntf->conn_id, -EIO);
+
+	return 0;
 }
 
 static const __u8 *
@@ -329,13 +357,18 @@ void nci_clear_target_list(struct nci_dev *ndev)
 	ndev->n_targets = 0;
 }
 
-static void nci_rf_discover_ntf_packet(struct nci_dev *ndev,
-				       const struct sk_buff *skb)
+static int nci_rf_discover_ntf_packet(struct nci_dev *ndev,
+				      const struct sk_buff *skb)
 {
 	struct nci_rf_discover_ntf ntf;
-	const __u8 *data = skb->data;
+	const __u8 *data;
 	bool add_target = true;
 
+	if (skb->len < sizeof(struct nci_rf_discover_ntf))
+		return -EINVAL;
+
+	data = skb->data;
+
 	ntf.rf_discovery_id = *data++;
 	ntf.rf_protocol = *data++;
 	ntf.rf_tech_and_mode = *data++;
@@ -390,6 +423,8 @@ static void nci_rf_discover_ntf_packet(struct nci_dev *ndev,
 		nfc_targets_found(ndev->nfc_dev, ndev->targets,
 				  ndev->n_targets);
 	}
+
+	return 0;
 }
 
 static int nci_extract_activation_params_iso_dep(struct nci_dev *ndev,
@@ -553,14 +588,19 @@ static int nci_store_ats_nfc_iso_dep(struct nci_dev *ndev,
 	return NCI_STATUS_OK;
 }
 
-static void nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
-					     const struct sk_buff *skb)
+static int nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
+					    const struct sk_buff *skb)
 {
 	struct nci_conn_info *conn_info;
 	struct nci_rf_intf_activated_ntf ntf;
-	const __u8 *data = skb->data;
+	const __u8 *data;
 	int err = NCI_STATUS_OK;
 
+	if (skb->len < sizeof(struct nci_rf_intf_activated_ntf))
+		return -EINVAL;
+
+	data = skb->data;
+
 	ntf.rf_discovery_id = *data++;
 	ntf.rf_interface = *data++;
 	ntf.rf_protocol = *data++;
@@ -667,7 +707,7 @@ static void nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
 	if (err == NCI_STATUS_OK) {
 		conn_info = ndev->rf_conn_info;
 		if (!conn_info)
-			return;
+			return 0;
 
 		conn_info->max_pkt_payload_len = ntf.max_data_pkt_payload_size;
 		conn_info->initial_num_credits = ntf.initial_num_credits;
@@ -721,19 +761,26 @@ static void nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
 				pr_err("error when signaling tm activation\n");
 		}
 	}
+
+	return 0;
 }
 
-static void nci_rf_deactivate_ntf_packet(struct nci_dev *ndev,
-					 const struct sk_buff *skb)
+static int nci_rf_deactivate_ntf_packet(struct nci_dev *ndev,
+					const struct sk_buff *skb)
 {
 	const struct nci_conn_info *conn_info;
-	const struct nci_rf_deactivate_ntf *ntf = (void *)skb->data;
+	const struct nci_rf_deactivate_ntf *ntf;
+
+	if (skb->len < sizeof(struct nci_rf_deactivate_ntf))
+		return -EINVAL;
+
+	ntf = (struct nci_rf_deactivate_ntf *)skb->data;
 
 	pr_debug("entry, type 0x%x, reason 0x%x\n", ntf->type, ntf->reason);
 
 	conn_info = ndev->rf_conn_info;
 	if (!conn_info)
-		return;
+		return 0;
 
 	/* drop tx data queue */
 	skb_queue_purge(&ndev->tx_q);
@@ -765,14 +812,20 @@ static void nci_rf_deactivate_ntf_packet(struct nci_dev *ndev,
 	}
 
 	nci_req_complete(ndev, NCI_STATUS_OK);
+
+	return 0;
 }
 
-static void nci_nfcee_discover_ntf_packet(struct nci_dev *ndev,
-					  const struct sk_buff *skb)
+static int nci_nfcee_discover_ntf_packet(struct nci_dev *ndev,
+					 const struct sk_buff *skb)
 {
 	u8 status = NCI_STATUS_OK;
-	const struct nci_nfcee_discover_ntf *nfcee_ntf =
-				(struct nci_nfcee_discover_ntf *)skb->data;
+	const struct nci_nfcee_discover_ntf *nfcee_ntf;
+
+	if (skb->len < sizeof(struct nci_nfcee_discover_ntf))
+		return -EINVAL;
+
+	nfcee_ntf = (struct nci_nfcee_discover_ntf *)skb->data;
 
 	/* NFCForum NCI 9.2.1 HCI Network Specific Handling
 	 * If the NFCC supports the HCI Network, it SHALL return one,
@@ -783,6 +836,8 @@ static void nci_nfcee_discover_ntf_packet(struct nci_dev *ndev,
 	ndev->cur_params.id = nfcee_ntf->nfcee_id;
 
 	nci_req_complete(ndev, status);
+
+	return 0;
 }
 
 void nci_ntf_packet(struct nci_dev *ndev, struct sk_buff *skb)
@@ -809,35 +864,43 @@ void nci_ntf_packet(struct nci_dev *ndev, struct sk_buff *skb)
 
 	switch (ntf_opcode) {
 	case NCI_OP_CORE_RESET_NTF:
-		nci_core_reset_ntf_packet(ndev, skb);
+		if (nci_core_reset_ntf_packet(ndev, skb))
+			goto end;
 		break;
 
 	case NCI_OP_CORE_CONN_CREDITS_NTF:
-		nci_core_conn_credits_ntf_packet(ndev, skb);
+		if (nci_core_conn_credits_ntf_packet(ndev, skb))
+			goto end;
 		break;
 
 	case NCI_OP_CORE_GENERIC_ERROR_NTF:
-		nci_core_generic_error_ntf_packet(ndev, skb);
+		if (nci_core_generic_error_ntf_packet(ndev, skb))
+			goto end;
 		break;
 
 	case NCI_OP_CORE_INTF_ERROR_NTF:
-		nci_core_conn_intf_error_ntf_packet(ndev, skb);
+		if (nci_core_conn_intf_error_ntf_packet(ndev, skb))
+			goto end;
 		break;
 
 	case NCI_OP_RF_DISCOVER_NTF:
-		nci_rf_discover_ntf_packet(ndev, skb);
+		if (nci_rf_discover_ntf_packet(ndev, skb))
+			goto end;
 		break;
 
 	case NCI_OP_RF_INTF_ACTIVATED_NTF:
-		nci_rf_intf_activated_ntf_packet(ndev, skb);
+		if (nci_rf_intf_activated_ntf_packet(ndev, skb))
+			goto end;
 		break;
 
 	case NCI_OP_RF_DEACTIVATE_NTF:
-		nci_rf_deactivate_ntf_packet(ndev, skb);
+		if (nci_rf_deactivate_ntf_packet(ndev, skb))
+			goto end;
 		break;
 
 	case NCI_OP_NFCEE_DISCOVER_NTF:
-		nci_nfcee_discover_ntf_packet(ndev, skb);
+		if (nci_nfcee_discover_ntf_packet(ndev, skb))
+			goto end;
 		break;
 
 	case NCI_OP_RF_NFCEE_ACTION_NTF:
-- 
2.51.0

Re: [PATCH net v4] net: nfc: nci: Add parameter validation for packet data

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Thu, 25 Sep 2025 18:58:46 +0530 you wrote:
> Syzbot reported an uninitialized value bug in nci_init_req, which was
> introduced by commit 5aca7966d2a7 ("Merge tag
> 'perf-tools-fixes-for-v6.17-2025-09-16' of
> git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools").
> 
> This bug arises due to very limited and poor input validation
> that was done at nic_valid_size(). This validation only
> validates the skb->len (directly reflects size provided at the
> userspace interface) with the length provided in the buffer
> itself (interpreted as NCI_HEADER). This leads to the processing
> of memory content at the address assuming the correct layout
> per what opcode requires there. This leads to the accesses to
> buffer of `skb_buff->data` which is not assigned anything yet.
> 
> [...]

Here is the summary with links:
  - [net,v4] net: nfc: nci: Add parameter validation for packet data
    https://git.kernel.org/netdev/net/c/9c328f54741b

You are awesome, thank you!
-- 
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