FAILED: patch "[PATCH] can: ems_usb: validate CPC message lengths" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 02925f51377f2a42a6724f00549167499c9302e5
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026080519-postwar-croak-21f6@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 02925f51377f2a42a6724f00549167499c9302e5 Mon Sep 17 00:00:00 2001
From: Pengpeng Hou <[email protected]>
Date: Mon, 6 Jul 2026 17:27:52 +0800
Subject: [PATCH] can: ems_usb: validate CPC message lengths

ems_usb_read_bulk_callback() walks CPC messages packed in one USB
receive buffer.

Check that each declared message fits in the URB payload. Also require the
type-specific payload to cover the fields used by the CAN, state, error and
overrun handlers.

Signed-off-by: Pengpeng Hou <[email protected]>
Link: https://patch.msgid.link/[email protected]
Fixes: 702171adeed3 ("ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface")
Cc: [email protected]
Signed-off-by: Marc Kleine-Budde <[email protected]>

diff --git a/drivers/net/can/usb/ems_usb.c b/drivers/net/can/usb/ems_usb.c
index 9b25dda7c183..24cf8f651f8f 100644
--- a/drivers/net/can/usb/ems_usb.c
+++ b/drivers/net/can/usb/ems_usb.c
@@ -409,6 +409,40 @@ static void ems_usb_rx_err(struct ems_usb *dev, struct ems_cpc_msg *msg)
 		netif_rx(skb);
 }
 
+static bool ems_usb_rx_msg_len_valid(struct ems_cpc_msg *msg)
+{
+	size_t len = msg->length;
+	size_t can_len;
+
+	switch (msg->type) {
+	case CPC_MSG_TYPE_CAN_STATE:
+		return len >= sizeof(msg->msg.can_state);
+
+	case CPC_MSG_TYPE_CAN_FRAME:
+	case CPC_MSG_TYPE_EXT_CAN_FRAME:
+	case CPC_MSG_TYPE_RTR_FRAME:
+	case CPC_MSG_TYPE_EXT_RTR_FRAME:
+		if (len < CPC_CAN_MSG_MIN_SIZE)
+			return false;
+
+		if (msg->type == CPC_MSG_TYPE_RTR_FRAME ||
+		    msg->type == CPC_MSG_TYPE_EXT_RTR_FRAME)
+			return true;
+
+		can_len = can_cc_dlc2len(msg->msg.can_msg.length & 0xf);
+		return len >= CPC_CAN_MSG_MIN_SIZE + can_len;
+
+	case CPC_MSG_TYPE_CAN_FRAME_ERROR:
+		return len >= sizeof(msg->msg.error);
+
+	case CPC_MSG_TYPE_OVERRUN:
+		return len >= sizeof(msg->msg.overrun);
+
+	default:
+		return true;
+	}
+}
+
 /*
  * callback for bulk IN urb
  */
@@ -451,6 +485,15 @@ static void ems_usb_read_bulk_callback(struct urb *urb)
 			}
 
 			msg = (struct ems_cpc_msg *)&ibuf[start];
+			if (msg->length >
+			    urb->actual_length - start - CPC_MSG_HEADER_LEN) {
+				netdev_err(netdev, "format error\n");
+				break;
+			}
+			if (!ems_usb_rx_msg_len_valid(msg)) {
+				netdev_err(netdev, "format error\n");
+				break;
+			}
 
 			switch (msg->type) {
 			case CPC_MSG_TYPE_CAN_STATE: