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Mon, 28 Sep 2026 19:33:15 +0000 (UTC) From: Marc Kleine-Budde To: netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, linux-can@vger.kernel.org, kernel@pengutronix.de, Kaixuan Li , Oliver Hartkopp , Quchaosheng , stable@vger.kernel.org, Marc Kleine-Budde Subject: [PATCH net 07/22] can: isotp: check the frame type, not just the length Date: Mon, 28 Sep 2026 20:45:14 +0200 Message-ID: <20260928193312.553632-8-mkl@pengutronix.de> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260928193312.553632-1-mkl@pengutronix.de> References: <20260928193312.553632-1-mkl@pengutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Kaixuan Li isotp_rcv() separates Classic CAN from CAN FD by skb->len alone: if (skb->len != so->ll.mtu) return; cf = (struct canfd_frame *)skb->data; A CAN XL frame with cxl->len 4 is CAN_MTU bytes, so it passes, and is then read as a canfd_frame whose len comes out of canxl_frame.flags: at least 0x80. Of the paths that follow, only the flow control one uses that length without bounding it first, so check_pad() walks to 255 over a 16-byte frame and the caller reports EBADMSG on an unrelated socket. bcm_rx_handler(), j1939_can_recv(), can_can_gw_rcv() and raw_rcv() check the frame type here, and can_dropped_invalid_skb() switches on skb->protocol on the transmit side. isotp_rcv() is the gap. Fixes: fb08cba12b52 ("can: canxl: update CAN infrastructure for CAN XL frames") Signed-off-by: Kaixuan Li Reviewed-by: Oliver Hartkopp Acked-by: Oliver Hartkopp Reviewed-by: Quchaosheng Link: https://patch.msgid.link/20260920035626.2581040-1-kaixuanli0131@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Marc Kleine-Budde --- net/can/isotp.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/can/isotp.c b/net/can/isotp.c index 155530aedce2..1e80eb2a6bae 100644 --- a/net/can/isotp.c +++ b/net/can/isotp.c @@ -755,6 +755,14 @@ static void isotp_rcv(struct sk_buff *skb, void *data) if (skb->len != so->ll.mtu) return; + /* check for correct CAN CC/FD frame content */ + if (so->ll.mtu == CAN_MTU) { + if (!can_is_can_skb(skb)) + return; + } else if (!can_is_canfd_skb(skb)) { + return; + } + cf = (struct canfd_frame *)skb->data; /* if enabled: check reception of my configured extended address */ -- 2.53.0