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

Deepak Sharma
2025-09-19T06:47:45Z

Syzbot reported an uninit-value bug at nci_init_req for commit
5aca7966d2a7 ("Merge tag 'perf-tools-fixes-for-v6.17-2025-09-16'..).

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
Signed-off-by: Deepak Sharma <deepak.sharma.472935@gmail.com>
---
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,
@@ -501,7 +536,7 @@ static int nci_store_general_bytes_nfc_dep(struct nci_dev *ndev,
case NCI_NFC_A_PASSIVE_POLL_MODE:
case NCI_NFC_F_PASSIVE_POLL_MODE:
ndev->remote_gb_len = min_t(__u8,
- (ntf->activation_params.poll_nfc_dep.atr_res_len
+ (ntf->activation_params.poll_nfc_dep.atr_res_len
- NFC_ATR_RES_GT_OFFSET),
NFC_ATR_RES_GB_MAXSIZE);
memcpy(ndev->remote_gb,
@@ -513,7 +548,7 @@ static int nci_store_general_bytes_nfc_dep(struct nci_dev *ndev,
case NCI_NFC_A_PASSIVE_LISTEN_MODE:
case NCI_NFC_F_PASSIVE_LISTEN_MODE:
ndev->remote_gb_len = min_t(__u8,
- (ntf->activation_params.listen_nfc_dep.atr_req_len
+ (ntf->activation_params.listen_nfc_dep.atr_req_len
- NFC_ATR_REQ_GT_OFFSET),
NFC_ATR_REQ_GB_MAXSIZE);
memcpy(ndev->remote_gb,
@@ -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