[PATCH v3] can: peak_usb: Add bounds check for USB channel index

[James Gao]

The channel control index ctrl_idx is derived from rx->len which comes
directly from a device USB payload. The mask 0x0f allows values 0-15,
but the array size of usb_if->dev[] is only 2. Values 2-15 cause heap
out-of-bounds read, eventually causing kernel panic in the IRQ context.

Add bounds checking for ctrl_idx before the array access in both
pcan_usb_pro_handle_canmsg() and pcan_usb_pro_handle_error().

Fixes: d8a199355f8f ("can: usb: PEAK-System Technik PCAN-USB Pro specific part")
Signed-off-by: James Gao <jamesgao5@xxxxxxxxxxx>
---


Hi Vincent, thank you for the feedback. 
I have separated the declaration and expression.

Changes in v2 -> v3:
- Separate declaration and expression

Changes in v1-> v2:
- Use ARRAY_SIZE(usb_if->dev) instead of PCAN_USBPRO_CHANNEL_COUNT
- Use -EINVAL instead of -ENOMEM
- Add newline between variable declaration and bounds check
- Wrap commit message

 drivers/net/can/usb/peak_usb/pcan_usb_pro.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_pro.c b/drivers/net/can/usb/peak_usb/pcan_usb_pro.c
index 4bfa8d0fbb32..ac22d7718299 100644
--- a/drivers/net/can/usb/peak_usb/pcan_usb_pro.c
+++ b/drivers/net/can/usb/peak_usb/pcan_usb_pro.c
@@ -534,12 +534,18 @@ static int pcan_usb_pro_handle_canmsg(struct pcan_usb_pro_interface *usb_if,
 				      struct pcan_usb_pro_rxmsg *rx)
 {
 	const unsigned int ctrl_idx = (rx->len >> 4) & 0x0f;
-	struct peak_usb_device *dev = usb_if->dev[ctrl_idx];
-	struct net_device *netdev = dev->netdev;
+	struct peak_usb_device *dev;
+	struct net_device *netdev;
 	struct can_frame *can_frame;
 	struct sk_buff *skb;
 	struct skb_shared_hwtstamps *hwts;
 
+	if (ctrl_idx >= ARRAY_SIZE(usb_if->dev))
+		return -EINVAL;
+
+	dev = usb_if->dev[ctrl_idx];
+	netdev = dev->netdev;
+
 	skb = alloc_can_skb(netdev, &can_frame);
 	if (!skb)
 		return -ENOMEM;
@@ -573,14 +579,20 @@ static int pcan_usb_pro_handle_error(struct pcan_usb_pro_interface *usb_if,
 {
 	const u16 raw_status = le16_to_cpu(er->status);
 	const unsigned int ctrl_idx = (er->channel >> 4) & 0x0f;
-	struct peak_usb_device *dev = usb_if->dev[ctrl_idx];
-	struct net_device *netdev = dev->netdev;
+	struct peak_usb_device *dev;
+	struct net_device *netdev;
 	struct can_frame *can_frame;
 	enum can_state new_state = CAN_STATE_ERROR_ACTIVE;
 	u8 err_mask = 0;
 	struct sk_buff *skb;
 	struct skb_shared_hwtstamps *hwts;
 
+	if (ctrl_idx >= ARRAY_SIZE(usb_if->dev))
+		return -EINVAL;
+
+	dev = usb_if->dev[ctrl_idx];
+	netdev = dev->netdev;
+
 	/* nothing should be sent while in BUS_OFF state */
 	if (dev->can.state == CAN_STATE_BUS_OFF)
 		return 0;
-- 
2.53.0