nci_store_general_bytes_nfc_dep() computes the General Bytes length by subtracting a fixed header offset from the peer-supplied atr_res_len (POLL) or atr_req_len (LISTEN) field: ndev->remote_gb_len = min_t(__u8, atr_res_len - NFC_ATR_RES_GT_OFFSET, /* offset = 15 */ NFC_ATR_RES_GB_MAXSIZE); Both length fields are __u8. When a malicious NFC-DEP peer sends an ATR_RES/ATR_REQ whose length is smaller than the fixed offset (< 15 or < 14 respectively), the subtraction wraps: atr_res_len = 0 -> (u8)(0 - 15) = 241 min_t(__u8, 241, NFC_ATR_RES_GB_MAXSIZE=47) = 47 The subsequent memcpy then reads 47 bytes beyond the valid activation parameter data into ndev->remote_gb[]. This buffer is later fed to nfc_llcp_parse_gb_tlv() as a TLV array. Reject the frame with NCI_STATUS_RF_PROTOCOL_ERROR when the length is below the required offset. The existing caller already logs and continues for other helpers that return a non-OK status from this switch, so no change is required on the caller side. Fixes: 767f19ae698e ("NFC: Implement NCI dep_link_up and dep_link_down") Cc: stable@vger.kernel.org Signed-off-by: Lekë Hapçiu --- net/nfc/nci/ntf.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c index 87f76a29f0ec..1a38f4666e97 100644 --- a/net/nfc/nci/ntf.c +++ b/net/nfc/nci/ntf.c @@ -653,6 +653,9 @@ static int nci_store_general_bytes_nfc_dep(struct nci_dev *ndev, switch (ntf->activation_rf_tech_and_mode) { case NCI_NFC_A_PASSIVE_POLL_MODE: case NCI_NFC_F_PASSIVE_POLL_MODE: + if (ntf->activation_params.poll_nfc_dep.atr_res_len < + NFC_ATR_RES_GT_OFFSET) + return NCI_STATUS_RF_PROTOCOL_ERROR; ndev->remote_gb_len = min_t(__u8, (ntf->activation_params.poll_nfc_dep.atr_res_len - NFC_ATR_RES_GT_OFFSET), @@ -665,6 +668,9 @@ 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: + if (ntf->activation_params.listen_nfc_dep.atr_req_len < + NFC_ATR_REQ_GT_OFFSET) + return NCI_STATUS_RF_PROTOCOL_ERROR; ndev->remote_gb_len = min_t(__u8, (ntf->activation_params.listen_nfc_dep.atr_req_len - NFC_ATR_REQ_GT_OFFSET), -- 2.51.0