linux-kernel - Re: [PATCH 8/8] usb_pcwd: remove superfluous usb

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Date:   Sat, 13 May 2023 11:52:21 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     oe-kbuild@...ts.linux.dev, Oliver Neukum <oneukum@...e.com>,
        wim@...ux-watchdog.org, linux@...ck-us.net,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
        Oliver Neukum <oneukum@...e.com>
Subject: Re: [PATCH 8/8] usb_pcwd: remove superfluous usb_device pointer

Hi Oliver,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Oliver-Neukum/pcwd_usb-stop-open-race-disconnect/20230427-223413
base:   linus/master
patch link:    https://lore.kernel.org/r/20230427133350.31064-9-oneukum%40suse.com
patch subject: [PATCH 8/8] usb_pcwd: remove superfluous usb_device pointer
config: parisc-randconfig-m041-20230509 (https://download.01.org/0day-ci/archive/20230512/202305122231.n8RlGMhT-lkp@intel.com/config)
compiler: hppa-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>
| Reported-by: Dan Carpenter <error27@...il.com>
| Link: https://lore.kernel.org/r/202305122231.n8RlGMhT-lkp@intel.com/

smatch warnings:
drivers/watchdog/pcwd_usb.c:215 usb_pcwd_send_command() warn: variable dereferenced before check 'usb_pcwd' (see line 211)

vim +/usb_pcwd +215 drivers/watchdog/pcwd_usb.c

143a2e54bf5321 drivers/watchdog/pcwd_usb.c      Wim Van Sebroeck   2009-03-18  206  static int usb_pcwd_send_command(struct usb_pcwd_private *usb_pcwd,
143a2e54bf5321 drivers/watchdog/pcwd_usb.c      Wim Van Sebroeck   2009-03-18  207  		unsigned char cmd, unsigned char *msb, unsigned char *lsb)
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  208  {
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  209  	int got_response, count;
5412df0bda90a2 drivers/watchdog/pcwd_usb.c      Guenter Roeck      2013-10-14  210  	unsigned char *buf;
41b4f0869562d7 drivers/watchdog/pcwd_usb.c      Oliver Neukum      2023-04-27 @211  	struct usb_device *udev = interface_to_usbdev(usb_pcwd->interface);
                                                                                                                                      ^^^^^^^^^^
Dereference.

^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  212  
143a2e54bf5321 drivers/watchdog/pcwd_usb.c      Wim Van Sebroeck   2009-03-18  213  	/* We will not send any commands if the USB PCWD device does
143a2e54bf5321 drivers/watchdog/pcwd_usb.c      Wim Van Sebroeck   2009-03-18  214  	 * not exist */
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16 @215  	if ((!usb_pcwd) || (!usb_pcwd->exists))
                                                                                            ^^^^^^^^^^^
Checked too late.

^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  216  		return -1;
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  217  
5412df0bda90a2 drivers/watchdog/pcwd_usb.c      Guenter Roeck      2013-10-14  218  	buf = kmalloc(6, GFP_KERNEL);
5412df0bda90a2 drivers/watchdog/pcwd_usb.c      Guenter Roeck      2013-10-14  219  	if (buf == NULL)
5412df0bda90a2 drivers/watchdog/pcwd_usb.c      Guenter Roeck      2013-10-14  220  		return 0;
5412df0bda90a2 drivers/watchdog/pcwd_usb.c      Guenter Roeck      2013-10-14  221  
143a2e54bf5321 drivers/watchdog/pcwd_usb.c      Wim Van Sebroeck   2009-03-18  222  	/* The USB PC Watchdog uses a 6 byte report format.
143a2e54bf5321 drivers/watchdog/pcwd_usb.c      Wim Van Sebroeck   2009-03-18  223  	 * The board currently uses only 3 of the six bytes of the report. */
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  224  	buf[0] = cmd;			/* Byte 0 = CMD */
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  225  	buf[1] = *msb;			/* Byte 1 = Data MSB */
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  226  	buf[2] = *lsb;			/* Byte 2 = Data LSB */
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  227  	buf[3] = buf[4] = buf[5] = 0;	/* All other bytes not used */
^1da177e4c3f41 drivers/char/watchdog/pcwd_usb.c Linus Torvalds     2005-04-16  228  
d7e92f7f768477 drivers/watchdog/pcwd_usb.c      Greg Kroah-Hartman 2013-12-19  229  	dev_dbg(&usb_pcwd->interface->dev,

-- 
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https://github.com/intel/lkp-tests