[PATCH v2] can: peak_usb: Add bounds check for USB channel index

[James Gao <jamesgao5@outlook.com>]

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@outlook.com>
---

Hi Marc,
	Thanks for the review for v1. Since this is not a security bug I have
	moved the discussion to public mail list. Changes in 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 | 8 ++++++++
 1 file changed, 8 insertions(+)

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..5b1e3501cfb8 100644
--- a/drivers/net/can/usb/peak_usb/pcan_usb_pro.c
+++ b/drivers/net/can/usb/peak_usb/pcan_usb_pro.c
@@ -534,6 +534,10 @@ 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;
+
+	if (ctrl_idx >= ARRAY_SIZE(usb_if->dev))
+		return -EINVAL;
+
 	struct peak_usb_device *dev = usb_if->dev[ctrl_idx];
 	struct net_device *netdev = dev->netdev;
 	struct can_frame *can_frame;
@@ -573,6 +577,10 @@ 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;
+
+	if (ctrl_idx >= ARRAY_SIZE(usb_if->dev))
+		return -EINVAL;
+
 	struct peak_usb_device *dev = usb_if->dev[ctrl_idx];
 	struct net_device *netdev = dev->netdev;
 	struct can_frame *can_frame;
-- 
2.53.0