usbnet: ipheth: check that DPE points past NCM header

By definition, a DPE points at the start of a network frame/datagram.
Thus it makes no sense for it to point at anything that's part of the
NCM header. It is not a security issue, but merely an indication of
a malformed DPE.

Enforce that all DPEs point at the data portion of the URB, past the
NCM header.

Fixes: a2d274c62e44 ("usbnet: ipheth: add CDC NCM support")
Cc: stable@vger.kernel.org
Signed-off-by: Foster Snowhill <forst@pen.gy>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/usb/ipheth.c b/drivers/net/usb/ipheth.c
index 45daae234cb856d921f66d53494983c44999daee..1ff5f7076ad531601083660d4b36b6b82dfc8a5e 100644 (file)
--- a/drivers/net/usb/ipheth.c
+++ b/drivers/net/usb/ipheth.c
@@ -242,7 +242,8 @@ static int ipheth_rcvbulk_callback_ncm(struct urb *urb)
        dpe = ncm0->dpe16;
        while (le16_to_cpu(dpe->wDatagramIndex) != 0 &&
               le16_to_cpu(dpe->wDatagramLength) != 0) {
-               if (le16_to_cpu(dpe->wDatagramIndex) >= urb->actual_length ||
+               if (le16_to_cpu(dpe->wDatagramIndex) < IPHETH_NCM_HEADER_SIZE ||
+                   le16_to_cpu(dpe->wDatagramIndex) >= urb->actual_length ||
                    le16_to_cpu(dpe->wDatagramLength) > urb->actual_length -
                    le16_to_cpu(dpe->wDatagramIndex)) {
                        dev->net->stats.rx_length_errors++;