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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Georgi Valkov , Simon Horman , Oliver Neukum , netdev@vger.kernel.org, linux-usb@vger.kernel.org Subject: [PATCH net v4 5/7] usbnet: ipheth: refactor NCM datagram loop Date: Sun, 5 Jan 2025 02:01:19 +0100 Message-ID: <20250105010121.12546-6-forst@pen.gy> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20250105010121.12546-1-forst@pen.gy> References: <20250105010121.12546-1-forst@pen.gy> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Proofpoint-GUID: FsV0s8q3dVdA-Frb-5dkAPXMrwn69fLs X-Proofpoint-ORIG-GUID: FsV0s8q3dVdA-Frb-5dkAPXMrwn69fLs X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-02_03,2025-01-02_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 adultscore=0 mlxlogscore=713 malwarescore=0 phishscore=0 bulkscore=0 suspectscore=0 mlxscore=0 clxscore=1030 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2308100000 definitions=main-2501050007 Introduce an rx_error label to reduce repetitions in the header signature checks. Store wDatagramIndex and wDatagramLength after endianness conversion to avoid repeated le16_to_cpu() calls. Rewrite the loop to return on a null trailing DPE, which is required by the CDC NCM spec. In case it is missing, fall through to rx_error. This change does not fix any particular issue. Its purpose is to simplify a subsequent commit that fixes a potential OoB read by limiting the maximum amount of processed DPEs. Fix an out-of-bounds DPE read, limit the number of processed DPEs to the amount that fits into the fixed-size NDP16 header. Signed-off-by: Foster Snowhill --- v4: Split from "usbnet: ipheth: refactor NCM datagram loop, fix DPE OoB read" in v3. This commit is responsible for the code refactor, while keeping the behaviour the same. v3: https://lore.kernel.org/netdev/20241123235432.821220-5-forst@pen.gy/ Split out from a monolithic patch in v2 as an atomic change. v2: https://lore.kernel.org/netdev/20240912211817.1707844-1-forst@pen.gy/ No code changes. Update commit message to further clarify that `ipheth` is not and does not aim to be a complete or spec-compliant CDC NCM implementation. v1: https://lore.kernel.org/netdev/20240907230108.978355-1-forst@pen.gy/ --- drivers/net/usb/ipheth.c | 42 ++++++++++++++++++++++------------------ 1 file changed, 23 insertions(+), 19 deletions(-) diff --git a/drivers/net/usb/ipheth.c b/drivers/net/usb/ipheth.c index 35f507db2c4a..03249208612e 100644 --- a/drivers/net/usb/ipheth.c +++ b/drivers/net/usb/ipheth.c @@ -224,9 +224,9 @@ static int ipheth_rcvbulk_callback_ncm(struct urb *urb) struct usb_cdc_ncm_ndp16 *ncm0; struct usb_cdc_ncm_dpe16 *dpe; struct ipheth_device *dev; + u16 dg_idx, dg_len; int retval = -EINVAL; char *buf; - int len; dev = urb->context; @@ -238,39 +238,43 @@ static int ipheth_rcvbulk_callback_ncm(struct urb *urb) ncmh = urb->transfer_buffer; if (ncmh->dwSignature != cpu_to_le32(USB_CDC_NCM_NTH16_SIGN) || /* On iOS, NDP16 directly follows NTH16 */ - ncmh->wNdpIndex != cpu_to_le16(sizeof(struct usb_cdc_ncm_nth16))) { - dev->net->stats.rx_errors++; - return retval; - } + ncmh->wNdpIndex != cpu_to_le16(sizeof(struct usb_cdc_ncm_nth16))) + goto rx_error; ncm0 = urb->transfer_buffer + sizeof(struct usb_cdc_ncm_nth16); - if (ncm0->dwSignature != cpu_to_le32(USB_CDC_NCM_NDP16_NOCRC_SIGN)) { - dev->net->stats.rx_errors++; - return retval; - } + if (ncm0->dwSignature != cpu_to_le32(USB_CDC_NCM_NDP16_NOCRC_SIGN)) + goto rx_error; dpe = ncm0->dpe16; - while (le16_to_cpu(dpe->wDatagramIndex) != 0 && - le16_to_cpu(dpe->wDatagramLength) != 0) { - if (le16_to_cpu(dpe->wDatagramIndex) < IPHETH_NCM_HEADER_SIZE || - le16_to_cpu(dpe->wDatagramIndex) >= urb->actual_length || - le16_to_cpu(dpe->wDatagramLength) > urb->actual_length - - le16_to_cpu(dpe->wDatagramIndex)) { + while (true) { + dg_idx = le16_to_cpu(dpe->wDatagramIndex); + dg_len = le16_to_cpu(dpe->wDatagramLength); + + /* Null DPE must be present after last datagram pointer entry + * (3.3.1 USB CDC NCM spec v1.0) + */ + if (dg_idx == 0 && dg_len == 0) + return 0; + + if (dg_idx < IPHETH_NCM_HEADER_SIZE || + dg_idx >= urb->actual_length || + dg_len > urb->actual_length - dg_idx) { dev->net->stats.rx_length_errors++; return retval; } - buf = urb->transfer_buffer + le16_to_cpu(dpe->wDatagramIndex); - len = le16_to_cpu(dpe->wDatagramLength); + buf = urb->transfer_buffer + dg_idx; - retval = ipheth_consume_skb(buf, len, dev); + retval = ipheth_consume_skb(buf, dg_len, dev); if (retval != 0) return retval; dpe++; } - return 0; +rx_error: + dev->net->stats.rx_errors++; + return retval; } static void ipheth_rcvbulk_callback(struct urb *urb)