[bug report] net: dsa: tag_ocelot_8021q: add support for PTP timestamping

[bug report] net: dsa: tag_ocelot_8021q: add support for PTP timestamping

[Dan Carpenter]

Hello Vladimir Oltean,

The patch 0a6f17c6ae21: "net: dsa: tag_ocelot_8021q: add support for
PTP timestamping" from Feb 14, 2021, leads to the following static
checker warning:

    drivers/net/dsa/ocelot/felix.c:1331 felix_check_xtr_pkt()
    error: uninitialized symbol 'err'.

    drivers/net/ethernet/mscc/ocelot_vsc7514.c:554 ocelot_xtr_irq_handler()
    error: uninitialized symbol 'err'

drivers/net/dsa/ocelot/felix.c
  1288  static bool felix_check_xtr_pkt(struct ocelot *ocelot, unsigned int ptp_type)
  1289  {
  1290          struct felix *felix = ocelot_to_felix(ocelot);
  1291          int err, grp = 0;
  1292  
  1293          if (felix->tag_proto != DSA_TAG_PROTO_OCELOT_8021Q)
  1294                  return false;
  1295  
  1296          if (!felix->info->quirk_no_xtr_irq)
  1297                  return false;
  1298  
  1299          if (ptp_type == PTP_CLASS_NONE)
  1300                  return false;
  1301  
  1302          while (ocelot_read(ocelot, QS_XTR_DATA_PRESENT) & BIT(grp)) {

What about if we don't ever enter this loop?

  1303                  struct sk_buff *skb;
  1304                  unsigned int type;
  1305  
  1306                  err = ocelot_xtr_poll_frame(ocelot, grp, &skb);
  1307                  if (err)
  1308                          goto out;
  1309  
  1310                  /* We trap to the CPU port module all PTP frames, but
  1311                   * felix_rxtstamp() only gets called for event frames.
  1312                   * So we need to avoid sending duplicate general
  1313                   * message frames by running a second BPF classifier
  1314                   * here and dropping those.
  1315                   */
  1316                  __skb_push(skb, ETH_HLEN);
  1317  
  1318                  type = ptp_classify_raw(skb);
  1319  
  1320                  __skb_pull(skb, ETH_HLEN);
  1321  
  1322                  if (type == PTP_CLASS_NONE) {
  1323                          kfree_skb(skb);
  1324                          continue;
  1325                  }
  1326  
  1327                  netif_rx(skb);
  1328          }
  1329  
  1330  out:
  1331          if (err < 0)
  1332                  ocelot_drain_cpu_queue(ocelot, 0);
  1333  

regards,
dan carpenter

Re: [bug report] net: dsa: tag_ocelot_8021q: add support for PTP timestamping

[Vladimir Oltean]

Hi Dan,

On Fri, Feb 19, 2021 at 12:54:10PM +0300, Dan Carpenter wrote:
> What about if we don't ever enter this loop?

This is a real bug, thanks for reporting. It would be good if you could
initialize err with zero.