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: