[kbuild] Re: [PATCH] drm/irq: Add irq as false detection

[Dan Carpenter]

Hi Tian,

url:    https://github.com/0day-ci/linux/commits/Tian-Tao/drm-irq-Add-irq-as-false-detection/20201102-192137 
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  3cea11cd5e3b00d91caf0b4730194039b45c5891
config: x86_64-randconfig-m001-20201102 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

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

New smatch warnings:
drivers/gpu/drm/drm_irq.c:175 drm_irq_uninstall() warn: variable dereferenced before check 'dev' (see line 175)

Old smatch warnings:
drivers/gpu/drm/drm_irq.c:149 drm_irq_install() warn: 'irq' not released on lines: 133.

vim +/dev +175 drivers/gpu/drm/drm_irq.c

84b1fd103dbbe01 drivers/char/drm/drm_irq.c Dave Airlie    2007-07-11  169  int drm_irq_uninstall(struct drm_device *dev)
^1da177e4c3f415 drivers/char/drm/drm_irq.c Linus Torvalds 2005-04-16  170  {
dc1336ff4fe08ae drivers/gpu/drm/drm_irq.c  Jesse Barnes   2009-01-06  171  	unsigned long irqflags;
4423843cde65232 drivers/gpu/drm/drm_irq.c  Ville Syrjälä  2013-10-04  172  	bool irq_enabled;
4423843cde65232 drivers/gpu/drm/drm_irq.c  Ville Syrjälä  2013-10-04  173  	int i;
^1da177e4c3f415 drivers/char/drm/drm_irq.c Linus Torvalds 2005-04-16  174  
fa889e8baa5377b drivers/gpu/drm/drm_irq.c  Tian Tao       2020-11-02 @175  	if (!dev->irq_enabled || !dev)
                                                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^
This is checking "dev" after dereferencing it.  Can "dev" even be NULL?

fa889e8baa5377b drivers/gpu/drm/drm_irq.c  Tian Tao       2020-11-02  176  		return 0;
fa889e8baa5377b drivers/gpu/drm/drm_irq.c  Tian Tao       2020-11-02  177  
^1da177e4c3f415 drivers/char/drm/drm_irq.c Linus Torvalds 2005-04-16  178  	irq_enabled = dev->irq_enabled;
4423843cde65232 drivers/gpu/drm/drm_irq.c  Ville Syrjälä  2013-10-04  179  	dev->irq_enabled = false;
^1da177e4c3f415 drivers/char/drm/drm_irq.c Linus Torvalds 2005-04-16  180  
dc1336ff4fe08ae drivers/gpu/drm/drm_irq.c  Jesse Barnes   2009-01-06  181  	/*
3bff93d64cf59f0 drivers/gpu/drm/drm_irq.c  Daniel Vetter  2015-02-22  182  	 * Wake up any waiters so they don't hang. This is just to paper over

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org 
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