Date:   Fri, 3 Dec 2021 17:09:55 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     kbuild@lists.01.org, Stephane Grosjean <s.grosjean@peak-system.com>
Cc:     lkp@intel.com, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org,
        Marc Kleine-Budde <mkl@pengutronix.de>
Subject: drivers/net/can/usb/peak_usb/pcan_usb.c:523 pcan_usb_decode_error()
 error: we previously assumed 'cf' could be null (see line 503)
Message-ID: <202112021833.wABxM5UN-lkp@intel.com>
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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   58e1100fdc5990b0cc0d4beaf2562a92e621ac7d
commit: c11dcee758302702a83c6e85e4c4c3d9af42d2b3 can: peak_usb: pcan_usb_decode_error(): upgrade handling of bus state changes
config: x86_64-randconfig-m001-20211202 (https://download.01.org/0day-ci/archive/20211202/202112021833.wABxM5UN-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

smatch warnings:
drivers/net/can/usb/peak_usb/pcan_usb.c:523 pcan_usb_decode_error() error: we previously assumed 'cf' could be null (see line 503)

vim +/cf +523 drivers/net/can/usb/peak_usb/pcan_usb.c

46be265d338833 Stephane Grosjean 2012-03-02  450  static int pcan_usb_decode_error(struct pcan_usb_msg_context *mc, u8 n,
46be265d338833 Stephane Grosjean 2012-03-02  451  				 u8 status_len)
46be265d338833 Stephane Grosjean 2012-03-02  452  {
46be265d338833 Stephane Grosjean 2012-03-02  453  	struct sk_buff *skb;
46be265d338833 Stephane Grosjean 2012-03-02  454  	struct can_frame *cf;
c11dcee7583027 Stephane Grosjean 2021-07-15  455  	enum can_state new_state = CAN_STATE_ERROR_ACTIVE;
46be265d338833 Stephane Grosjean 2012-03-02  456  
46be265d338833 Stephane Grosjean 2012-03-02  457  	/* ignore this error until 1st ts received */
46be265d338833 Stephane Grosjean 2012-03-02  458  	if (n == PCAN_USB_ERROR_QOVR)
46be265d338833 Stephane Grosjean 2012-03-02  459  		if (!mc->pdev->time_ref.tick_count)
46be265d338833 Stephane Grosjean 2012-03-02  460  			return 0;
46be265d338833 Stephane Grosjean 2012-03-02  461  
c11dcee7583027 Stephane Grosjean 2021-07-15  462  	/* allocate an skb to store the error frame */
c11dcee7583027 Stephane Grosjean 2021-07-15  463  	skb = alloc_can_err_skb(mc->netdev, &cf);
46be265d338833 Stephane Grosjean 2012-03-02  464  
c11dcee7583027 Stephane Grosjean 2021-07-15  465  	if (n & PCAN_USB_ERROR_RXQOVR) {
c11dcee7583027 Stephane Grosjean 2021-07-15  466  		/* data overrun interrupt */
c11dcee7583027 Stephane Grosjean 2021-07-15  467  		netdev_dbg(mc->netdev, "data overrun interrupt\n");
c11dcee7583027 Stephane Grosjean 2021-07-15  468  		mc->netdev->stats.rx_over_errors++;
c11dcee7583027 Stephane Grosjean 2021-07-15  469  		mc->netdev->stats.rx_errors++;
c11dcee7583027 Stephane Grosjean 2021-07-15  470  		if (cf) {

Check for NULL

c11dcee7583027 Stephane Grosjean 2021-07-15  471  			cf->can_id |= CAN_ERR_CRTL;
c11dcee7583027 Stephane Grosjean 2021-07-15  472  			cf->data[1] |= CAN_ERR_CRTL_RX_OVERFLOW;
46be265d338833 Stephane Grosjean 2012-03-02  473  		}
46be265d338833 Stephane Grosjean 2012-03-02  474  	}
46be265d338833 Stephane Grosjean 2012-03-02  475  
c11dcee7583027 Stephane Grosjean 2021-07-15  476  	if (n & PCAN_USB_ERROR_TXQFULL)
c11dcee7583027 Stephane Grosjean 2021-07-15  477  		netdev_dbg(mc->netdev, "device Tx queue full)\n");
c11dcee7583027 Stephane Grosjean 2021-07-15  478  
46be265d338833 Stephane Grosjean 2012-03-02  479  	if (n & PCAN_USB_ERROR_BUS_OFF) {
46be265d338833 Stephane Grosjean 2012-03-02  480  		new_state = CAN_STATE_BUS_OFF;
c11dcee7583027 Stephane Grosjean 2021-07-15  481  	} else if (n & PCAN_USB_ERROR_BUS_HEAVY) {
c11dcee7583027 Stephane Grosjean 2021-07-15  482  		new_state = ((mc->pdev->bec.txerr >= 128) ||
c11dcee7583027 Stephane Grosjean 2021-07-15  483  			     (mc->pdev->bec.rxerr >= 128)) ?
c11dcee7583027 Stephane Grosjean 2021-07-15  484  				CAN_STATE_ERROR_PASSIVE :
c11dcee7583027 Stephane Grosjean 2021-07-15  485  				CAN_STATE_ERROR_WARNING;
c11dcee7583027 Stephane Grosjean 2021-07-15  486  	} else {
c11dcee7583027 Stephane Grosjean 2021-07-15  487  		new_state = CAN_STATE_ERROR_ACTIVE;
46be265d338833 Stephane Grosjean 2012-03-02  488  	}
46be265d338833 Stephane Grosjean 2012-03-02  489  
c11dcee7583027 Stephane Grosjean 2021-07-15  490  	/* handle change of state */
c11dcee7583027 Stephane Grosjean 2021-07-15  491  	if (new_state != mc->pdev->dev.can.state) {
c11dcee7583027 Stephane Grosjean 2021-07-15  492  		enum can_state tx_state =
c11dcee7583027 Stephane Grosjean 2021-07-15  493  			(mc->pdev->bec.txerr >= mc->pdev->bec.rxerr) ?
c11dcee7583027 Stephane Grosjean 2021-07-15  494  				new_state : 0;
c11dcee7583027 Stephane Grosjean 2021-07-15  495  		enum can_state rx_state =
c11dcee7583027 Stephane Grosjean 2021-07-15  496  			(mc->pdev->bec.txerr <= mc->pdev->bec.rxerr) ?
c11dcee7583027 Stephane Grosjean 2021-07-15  497  				new_state : 0;
46be265d338833 Stephane Grosjean 2012-03-02  498  
c11dcee7583027 Stephane Grosjean 2021-07-15  499  		can_change_state(mc->netdev, cf, tx_state, rx_state);
46be265d338833 Stephane Grosjean 2012-03-02  500  
c11dcee7583027 Stephane Grosjean 2021-07-15  501  		if (new_state == CAN_STATE_BUS_OFF) {
46be265d338833 Stephane Grosjean 2012-03-02  502  			can_bus_off(mc->netdev);
c11dcee7583027 Stephane Grosjean 2021-07-15 @503  		} else if (cf && (cf->can_id & CAN_ERR_CRTL)) {

Check for NULL

c11dcee7583027 Stephane Grosjean 2021-07-15  504  			/* Supply TX/RX error counters in case of
c11dcee7583027 Stephane Grosjean 2021-07-15  505  			 * controller error.
c11dcee7583027 Stephane Grosjean 2021-07-15  506  			 */
ea8b33bde76c8f Stephane Grosjean 2019-12-06  507  			cf->data[6] = mc->pdev->bec.txerr;
ea8b33bde76c8f Stephane Grosjean 2019-12-06  508  			cf->data[7] = mc->pdev->bec.rxerr;
ea8b33bde76c8f Stephane Grosjean 2019-12-06  509  		}
46be265d338833 Stephane Grosjean 2012-03-02  510  	}
46be265d338833 Stephane Grosjean 2012-03-02  511  
c11dcee7583027 Stephane Grosjean 2021-07-15  512  	if (!skb)
c11dcee7583027 Stephane Grosjean 2021-07-15  513  		return -ENOMEM;
46be265d338833 Stephane Grosjean 2012-03-02  514  
46be265d338833 Stephane Grosjean 2012-03-02  515  	if (status_len & PCAN_USB_STATUSLEN_TIMESTAMP) {
c9faaa09e2a133 Oliver Hartkopp   2012-11-21  516  		struct skb_shared_hwtstamps *hwts = skb_hwtstamps(skb);
c9faaa09e2a133 Oliver Hartkopp   2012-11-21  517  
d5888a1e75c799 Arnd Bergmann     2017-11-03  518  		peak_usb_get_ts_time(&mc->pdev->time_ref, mc->ts16,
d5888a1e75c799 Arnd Bergmann     2017-11-03  519  				     &hwts->hwtstamp);
46be265d338833 Stephane Grosjean 2012-03-02  520  	}
46be265d338833 Stephane Grosjean 2012-03-02  521  
46be265d338833 Stephane Grosjean 2012-03-02  522  	mc->netdev->stats.rx_packets++;
c7b74967799b1a Oliver Hartkopp   2020-11-20 @523  	mc->netdev->stats.rx_bytes += cf->len;
                                                                                      ^^^^^^^^
No check for NULL.

1c0ee046957648 Marc Kleine-Budde 2015-07-11  524  	netif_rx(skb);
46be265d338833 Stephane Grosjean 2012-03-02  525  
46be265d338833 Stephane Grosjean 2012-03-02  526  	return 0;
46be265d338833 Stephane Grosjean 2012-03-02  527  }

---
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