net: cdc_ncm: splitting rx_fixup for code reuse

Verifying and handling received MBIM and NCM frames will need
to be different in three areas:
 - verifying the NDP signature
 - checking valid datagram length
 - datagram header manipulation

This makes it inconvenient to share rx_fixup in whole.  But
some verification parts are common.  Split these out in separate
functions.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 34069346544f3e89f105b9f696d2faa350a2b696..6688a15e044d96a411a9f6de81fbda13933b4b74 100644 (file)
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -966,19 +966,12 @@ error:
        return NULL;
 }
 
-static int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in)
+/* verify NTB header and return offset of first NDP, or negative error */
+static int cdc_ncm_rx_verify_nth16(struct cdc_ncm_ctx *ctx, struct sk_buff *skb_in)
 {
-       struct sk_buff *skb;
-       struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
-       int len;
-       int nframes;
-       int x;
-       int offset;
        struct usb_cdc_ncm_nth16 *nth16;
-       struct usb_cdc_ncm_ndp16 *ndp16;
-       struct usb_cdc_ncm_dpe16 *dpe16;
-       int ndpoffset;
-       int loopcount = 50; /* arbitrary max preventing infinite loop */
+       int len;
+       int ret = -EINVAL;
 
        if (ctx == NULL)
                goto error;
@@ -1012,40 +1005,74 @@ static int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in)
        }
        ctx->rx_seq = le16_to_cpu(nth16->wSequence);
 
-       ndpoffset = le16_to_cpu(nth16->wNdpIndex);
-next_ndp:
+       ret = le16_to_cpu(nth16->wNdpIndex);
+error:
+       return ret;
+}
+
+/* verify NDP header and return number of datagrams, or negative error */
+static int cdc_ncm_rx_verify_ndp16(struct sk_buff *skb_in, int ndpoffset)
+{
+       struct usb_cdc_ncm_ndp16 *ndp16;
+       int ret = -EINVAL;
+
        if ((ndpoffset + sizeof(struct usb_cdc_ncm_ndp16)) > skb_in->len) {
                pr_debug("invalid NDP offset  <%u>\n", ndpoffset);
                goto error;
        }
        ndp16 = (struct usb_cdc_ncm_ndp16 *)(skb_in->data + ndpoffset);
 
-       if (le32_to_cpu(ndp16->dwSignature) != USB_CDC_NCM_NDP16_NOCRC_SIGN) {
-               pr_debug("invalid DPT16 signature <%u>\n",
-                                       le32_to_cpu(ndp16->dwSignature));
-               goto err_ndp;
-       }
-
        if (le16_to_cpu(ndp16->wLength) < USB_CDC_NCM_NDP16_LENGTH_MIN) {
                pr_debug("invalid DPT16 length <%u>\n",
                                        le32_to_cpu(ndp16->dwSignature));
-               goto err_ndp;
+               goto error;
        }
 
-       nframes = ((le16_to_cpu(ndp16->wLength) -
+       ret = ((le16_to_cpu(ndp16->wLength) -
                                        sizeof(struct usb_cdc_ncm_ndp16)) /
                                        sizeof(struct usb_cdc_ncm_dpe16));
-       nframes--; /* we process NDP entries except for the last one */
-
-       ndpoffset += sizeof(struct usb_cdc_ncm_ndp16);
+       ret--; /* we process NDP entries except for the last one */
 
-       if ((ndpoffset + nframes * (sizeof(struct usb_cdc_ncm_dpe16))) >
+       if ((sizeof(struct usb_cdc_ncm_ndp16) + ret * (sizeof(struct usb_cdc_ncm_dpe16))) >
                                                                skb_in->len) {
-               pr_debug("Invalid nframes = %d\n", nframes);
-               goto err_ndp;
+               pr_debug("Invalid nframes = %d\n", ret);
+               ret = -EINVAL;
        }
 
-       dpe16 = (struct usb_cdc_ncm_dpe16 *)(skb_in->data + ndpoffset);
+error:
+       return ret;
+}
+
+static int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in)
+{
+       struct sk_buff *skb;
+       struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
+       int len;
+       int nframes;
+       int x;
+       int offset;
+       struct usb_cdc_ncm_ndp16 *ndp16;
+       struct usb_cdc_ncm_dpe16 *dpe16;
+       int ndpoffset;
+       int loopcount = 50; /* arbitrary max preventing infinite loop */
+
+       ndpoffset = cdc_ncm_rx_verify_nth16(ctx, skb_in);
+       if (ndpoffset < 0)
+               goto error;
+
+next_ndp:
+       nframes = cdc_ncm_rx_verify_ndp16(skb_in, ndpoffset);
+       if (nframes < 0)
+               goto error;
+
+       ndp16 = (struct usb_cdc_ncm_ndp16 *)(skb_in->data + ndpoffset);
+
+       if (le32_to_cpu(ndp16->dwSignature) != USB_CDC_NCM_NDP16_NOCRC_SIGN) {
+               pr_debug("invalid DPT16 signature <%u>\n",
+                        le32_to_cpu(ndp16->dwSignature));
+               goto err_ndp;
+       }
+       dpe16 = ndp16->dpe16;
 
        for (x = 0; x < nframes; x++, dpe16++) {
                offset = le16_to_cpu(dpe16->wDatagramIndex);