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
Regards,
---
Stéphane Grosjean
PEAK-System France
132, rue André Bisiaux
F-54320 MAXEVILLE
Tél : +(33) 9.72.54.51.97
De : Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Envoyé : jeudi 13 août 2020 16:06
À : Wolfgang Grandegger <wg@xxxxxxxxxxxxxx>; Stéphane Grosjean <s.grosjean@xxxxxxxxxxxxxxx>
Cc : Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Andri Yngvason <andri.yngvason@xxxxxxxxx>; Oliver Hartkopp <socketcan@xxxxxxxxxxxx>; linux-can@xxxxxxxxxxxxxxx <linux-can@xxxxxxxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx <netdev@xxxxxxxxxxxxxxx>; kernel-janitors@xxxxxxxxxxxxxxx <kernel-janitors@xxxxxxxxxxxxxxx>
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 <dan.carpenter@xxxxxxxxxx>
---
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
--
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