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Date: Wed, 8 Apr 2026 22:31:13 +0000 Message-Id: <20260408223113.2009304-1-ashutoshdesai993@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Both nfc_hci_recv_from_llc() and nfc_hci_msg_rx_work() read byte 1 of an sk_buff (the HCP message header field) without first verifying the buffer contains at least NFC_HCI_HCP_HEADER_LEN (2) bytes. The SHDLC LLC layer only filters zero-length frames; a single-byte I-frame from a malicious NFC peer therefore reaches the HCI reassembly path where packet->message.header is read one byte past the valid data. The same issue is present in the NCI HCI implementation (nci/hci.c) via nci_hci_data_received_cb() and nci_hci_msg_rx_work(). Add an explicit length check before accessing the message header at all four locations, freeing the skb on malformed input. Signed-off-by: Ashutosh Desai --- net/nfc/hci/core.c | 9 +++++++++ net/nfc/nci/hci.c | 9 +++++++++ 2 files changed, 18 insertions(+) diff --git a/net/nfc/hci/core.c b/net/nfc/hci/core.c index 0d33c81a1..13d10b841 100644 --- a/net/nfc/hci/core.c +++ b/net/nfc/hci/core.c @@ -134,6 +134,10 @@ static void nfc_hci_msg_rx_work(struct work_struct *wo= rk) u8 instruction; =20 while ((skb =3D skb_dequeue(&hdev->msg_rx_queue)) !=3D NULL) { + if (skb->len < NFC_HCI_HCP_HEADER_LEN) { + kfree_skb(skb); + continue; + } pipe =3D skb->data[0]; skb_pull(skb, NFC_HCI_HCP_PACKET_HEADER_LEN); message =3D (struct hcp_message *)skb->data; @@ -904,6 +908,11 @@ static void nfc_hci_recv_from_llc(struct nfc_hci_dev *= hdev, struct sk_buff *skb) * unblock waiting cmd context. Otherwise, enqueue to dispatch * in separate context where handler can also execute command. */ + if (hcp_skb->len < NFC_HCI_HCP_HEADER_LEN) { + kfree_skb(hcp_skb); + return; + } + packet =3D (struct hcp_packet *)hcp_skb->data; type =3D HCP_MSG_GET_TYPE(packet->message.header); if (type =3D=3D NFC_HCI_HCP_RESPONSE) { diff --git a/net/nfc/nci/hci.c b/net/nfc/nci/hci.c index 40ae8e5a7..2a6432878 100644 --- a/net/nfc/nci/hci.c +++ b/net/nfc/nci/hci.c @@ -412,6 +412,10 @@ static void nci_hci_msg_rx_work(struct work_struct *wo= rk) =20 for (; (skb =3D skb_dequeue(&hdev->msg_rx_queue)); kcov_remote_stop()) { kcov_remote_start_common(skb_get_kcov_handle(skb)); + if (skb->len < NCI_HCI_HCP_HEADER_LEN) { + kfree_skb(skb); + continue; + } pipe =3D NCI_HCP_MSG_GET_PIPE(skb->data[0]); skb_pull(skb, NCI_HCI_HCP_PACKET_HEADER_LEN); message =3D (struct nci_hcp_message *)skb->data; @@ -482,6 +486,11 @@ void nci_hci_data_received_cb(void *context, * unblock waiting cmd context. Otherwise, enqueue to dispatch * in separate context where handler can also execute command. */ + if (hcp_skb->len < NCI_HCI_HCP_HEADER_LEN) { + kfree_skb(hcp_skb); + return; + } + packet =3D (struct nci_hcp_packet *)hcp_skb->data; type =3D NCI_HCP_MSG_GET_TYPE(packet->message.header); if (type =3D=3D NCI_HCI_HCP_RESPONSE) { --=20 2.34.1