linux-kernel - Re: 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)

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Date:   Fri, 3 Dec 2021 18:14:44 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     kbuild@...ts.01.org,
        Stephane Grosjean <s.grosjean@...k-system.com>, lkp@...el.com,
        kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: 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)

On Fri, Dec 03, 2021 at 03:58:51PM +0100, Marc Kleine-Budde wrote:
> > 
> > 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);
> 
> alloc_can_err_skb() ->
> alloc_canfd_skb()
> 
> https://elixir.bootlin.com/linux/v5.15/source/drivers/net/can/dev/skb.c#L210
> 
> If skb is NULL, cf is set to NULL, too.

Yeah.  Sorry about that.  The kbuild-bot doesn't do much cross function
analysis (none for functions that are not inline).  I saw that this
patch was old and could easily have checked it on my system which has
the cross function DB but I was in a rush.  :/  My bad.  Will try be a
more diligent person next time.

regards,
dan carpenter