net: nfc: nci: Add parameter validation for packet data

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>
Link: https://patch.msgid.link/20250925132846.213425-1-deepak.sharma.472935@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c
index a818eff27e6bc2555a189d9dbbd82bd6ca39680d..418b84e2b2605f440e8a3607e22adf08a4d95d08 100644 (file)
--- 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 @@ exit:
        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 @@ listen:
                                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: