Re: [PATCH net] can: peak_usb: add range checking in decode operations
From: Oliver Hartkopp <socketcan@hartkopp.net>
Date: 2020-10-14 17:49:05
Also in:
kernel-janitors, linux-can
Hi Stephane, On 14.10.20 15:22, Stéphane Grosjean wrote:
Hello Dan, Don't know if this patch is still relevant, but: - there is absolutely no reason for the device firmware to provide a channel index greater than or equal to 2, because the IP core of these USB devices handles 2 channels only. Anyway, these changes are correct. - considering the verification of the length "cfd->len" on the other hand, this one comes directly from can_send() via dev_queue_xmit() AFAIK and it seems to me that the underlying driver can assume that its value is smaller than 64.
In fact there are many inbound checks e.g. with can_dropped_invalid_skb() to make sure the network layer gets proper CAN skbs (with ETH_P_CAN(FD) ethertypes). On the outgoing path the CAN driver gets these ETH_P_CAN(FD) CAN skbs an just copies the CAN ID and the up to 64 bytes of data from that skb. But remember that you can also generate CAN frames via AF_PACKET sockets which does not perform the sanity checks from can_send(): https://github.com/linux-can/can-tests/blob/master/netlayer/tst-packet.c Copying 64 byte from the skb into an I/O attached CAN controller is always a safe operation - but when you send the content through another medium (e.g. USB) the length values should be checked. Best regards, Oliver
quoted hunk ↗ jump to hunk
Regards, --- Stéphane Grosjean PEAK-System France 132, rue André Bisiaux F-54320 MAXEVILLE Tél : +(33) 9.72.54.51.97 De : Dan Carpenter [off-list ref] Envoyé : jeudi 13 août 2020 16:06 À : Wolfgang Grandegger [off-list ref]; Stéphane Grosjean [off-list ref] Cc : Marc Kleine-Budde [off-list ref]; David S. Miller [off-list ref]; Jakub Kicinski [off-list ref]; Andri Yngvason [off-list ref]; Oliver Hartkopp [off-list ref]; linux-can@vger.kernel.org [off-list ref]; netdev@vger.kernel.org [off-list ref]; kernel-janitors@vger.kernel.org [off-list ref] Objet : [PATCH net] can: peak_usb: add range checking in decode operations These values come from skb->data so Smatch considers them untrusted. I believe Smatch is correct but I don't have a way to test this. The usb_if->dev[] array has 2 elements but the index is in the 0-15 range without checks. The cfd->len can be up to 255 but the maximum valid size is CANFD_MAX_DLEN (64) so that could lead to memory corruption. Fixes: 0a25e1f4f185 ("can: peak_usb: add support for PEAK new CANFD USB adapters") Signed-off-by: Dan Carpenter <redacted> --- drivers/net/can/usb/peak_usb/pcan_usb_fd.c | 48 +++++++++++++++++----- 1 file changed, 37 insertions(+), 11 deletions(-)diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_fd.c b/drivers/net/can/usb/peak_usb/pcan_usb_fd.c index 47cc1ff5b88e..dee3e689b54d 100644 --- a/drivers/net/can/usb/peak_usb/pcan_usb_fd.c +++ b/drivers/net/can/usb/peak_usb/pcan_usb_fd.c@@ -468,12 +468,18 @@ static int pcan_usb_fd_decode_canmsg(struct pcan_usb_fd_if *usb_if, struct pucan_msg *rx_msg) { struct pucan_rx_msg *rm = (struct pucan_rx_msg *)rx_msg; - struct peak_usb_device *dev = usb_if->dev[pucan_msg_get_channel(rm)]; - struct net_device *netdev = dev->netdev; + struct peak_usb_device *dev; + struct net_device *netdev; struct canfd_frame *cfd; struct sk_buff *skb; const u16 rx_msg_flags = le16_to_cpu(rm->flags); + if (pucan_msg_get_channel(rm) >= ARRAY_SIZE(usb_if->dev)) + return -ENOMEM; + + dev = usb_if->dev[pucan_msg_get_channel(rm)]; + netdev = dev->netdev; + if (rx_msg_flags & PUCAN_MSG_EXT_DATA_LEN) { /* CANFD frame case */ skb = alloc_canfd_skb(netdev, &cfd);@@ -519,15 +525,21 @@ static int pcan_usb_fd_decode_status(struct pcan_usb_fd_if *usb_if, struct pucan_msg *rx_msg) { struct pucan_status_msg *sm = (struct pucan_status_msg *)rx_msg; - struct peak_usb_device *dev = usb_if->dev[pucan_stmsg_get_channel(sm)]; - struct pcan_usb_fd_device *pdev = - container_of(dev, struct pcan_usb_fd_device, dev); + struct pcan_usb_fd_device *pdev; enum can_state new_state = CAN_STATE_ERROR_ACTIVE; enum can_state rx_state, tx_state; - struct net_device *netdev = dev->netdev; + struct peak_usb_device *dev; + struct net_device *netdev; struct can_frame *cf; struct sk_buff *skb; + if (pucan_stmsg_get_channel(sm) >= ARRAY_SIZE(usb_if->dev)) + return -ENOMEM; + + dev = usb_if->dev[pucan_stmsg_get_channel(sm)]; + pdev = container_of(dev, struct pcan_usb_fd_device, dev); + netdev = dev->netdev; + /* nothing should be sent while in BUS_OFF state */ if (dev->can.state == CAN_STATE_BUS_OFF) return 0;@@ -579,9 +591,14 @@ static int pcan_usb_fd_decode_error(struct pcan_usb_fd_if *usb_if, struct pucan_msg *rx_msg) { struct pucan_error_msg *er = (struct pucan_error_msg *)rx_msg; - struct peak_usb_device *dev = usb_if->dev[pucan_ermsg_get_channel(er)]; - struct pcan_usb_fd_device *pdev = - container_of(dev, struct pcan_usb_fd_device, dev); + struct pcan_usb_fd_device *pdev; + struct peak_usb_device *dev; + + if (pucan_ermsg_get_channel(er) >= ARRAY_SIZE(usb_if->dev)) + return -EINVAL; + + dev = usb_if->dev[pucan_ermsg_get_channel(er)]; + pdev = container_of(dev, struct pcan_usb_fd_device, dev); /* keep a trace of tx and rx error counters for later use */ pdev->bec.txerr = er->tx_err_cnt;@@ -595,11 +612,17 @@ static int pcan_usb_fd_decode_overrun(struct pcan_usb_fd_if *usb_if, struct pucan_msg *rx_msg) { struct pcan_ufd_ovr_msg *ov = (struct pcan_ufd_ovr_msg *)rx_msg; - struct peak_usb_device *dev = usb_if->dev[pufd_omsg_get_channel(ov)]; - struct net_device *netdev = dev->netdev; + struct peak_usb_device *dev; + struct net_device *netdev; struct can_frame *cf; struct sk_buff *skb; + if (pufd_omsg_get_channel(ov) >= ARRAY_SIZE(usb_if->dev)) + return -EINVAL; + + dev = usb_if->dev[pufd_omsg_get_channel(ov)]; + netdev = dev->netdev; + /* allocate an skb to store the error frame */ skb = alloc_can_err_skb(netdev, &cf); if (!skb)@@ -716,6 +739,9 @@ static int pcan_usb_fd_encode_msg(struct peak_usb_device *dev, u16 tx_msg_size, tx_msg_flags; u8 can_dlc; + if (cfd->len > CANFD_MAX_DLEN) + return -EINVAL; + tx_msg_size = ALIGN(sizeof(struct pucan_tx_msg) + cfd->len, 4); tx_msg->size = cpu_to_le16(tx_msg_size); tx_msg->type = cpu_to_le16(PUCAN_MSG_CAN_TX); --2.28.0 -- PEAK-System Technik GmbH Sitz der Gesellschaft Darmstadt - HRB 9183 Geschaeftsfuehrung: Alexander Gach / Uwe Wilhelm Unsere Datenschutzerklaerung mit wichtigen Hinweisen zur Behandlung personenbezogener Daten finden Sie unter www.peak-system.com/Datenschutz.483.0.html