[drm-i915:for-linux-next 11/18] drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)

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* [drm-i915:for-linux-next 11/18] drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)
@ 2025-08-15 20:09 ` Dan Carpenter
  0 siblings, 0 replies; 5+ messages in thread
From: kernel test robot @ 2025-08-15 17:01 UTC (permalink / raw)
  To: oe-kbuild; +Cc: lkp, Dan Carpenter

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
TO: Jani Nikula <jani.nikula@intel.com>
CC: Gustavo Sousa <gustavo.sousa@intel.com>

tree:   https://gitlab.freedesktop.org/drm/i915/kernel for-linux-next
head:   63e0b17ae79a4365e874d7e2ff3816db2e6d55b5
commit: d2e184f8e16ab85876ddcc0779358fbfe5162414 [11/18] drm/i915/switcheroo: pass display to HAS_DISPLAY()
:::::: branch date: 6 hours ago
:::::: commit date: 31 hours ago
config: i386-randconfig-141-20250815 (https://download.01.org/0day-ci/archive/20250816/202508160035.hmzuKiww-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202508160035.hmzuKiww-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)
drivers/gpu/drm/i915/i915_switcheroo.c:55 i915_switcheroo_can_switch() warn: variable dereferenced before check 'i915' (see line 48)

vim +/i915 +21 drivers/gpu/drm/i915/i915_switcheroo.c

63bf8301aac492 Jani Nikula       2019-10-04  13  
63bf8301aac492 Jani Nikula       2019-10-04  14  static void i915_switcheroo_set_state(struct pci_dev *pdev,
63bf8301aac492 Jani Nikula       2019-10-04  15  				      enum vga_switcheroo_state state)
63bf8301aac492 Jani Nikula       2019-10-04  16  {
63bf8301aac492 Jani Nikula       2019-10-04  17  	struct drm_i915_private *i915 = pdev_to_i915(pdev);
d2e184f8e16ab8 Jani Nikula       2025-08-06 @18  	struct intel_display *display = i915->display;
63bf8301aac492 Jani Nikula       2019-10-04  19  	pm_message_t pmm = { .event = PM_EVENT_SUSPEND };
63bf8301aac492 Jani Nikula       2019-10-04  20  
63bf8301aac492 Jani Nikula       2019-10-04 @21  	if (!i915) {
63bf8301aac492 Jani Nikula       2019-10-04  22  		dev_err(&pdev->dev, "DRM not initialized, aborting switch.\n");
63bf8301aac492 Jani Nikula       2019-10-04  23  		return;
63bf8301aac492 Jani Nikula       2019-10-04  24  	}
d2e184f8e16ab8 Jani Nikula       2025-08-06  25  	if (!HAS_DISPLAY(display)) {
a273e95721e968 Thomas Zimmermann 2023-01-16  26  		dev_err(&pdev->dev, "Device state not initialized, aborting switch.\n");
a273e95721e968 Thomas Zimmermann 2023-01-16  27  		return;
a273e95721e968 Thomas Zimmermann 2023-01-16  28  	}
63bf8301aac492 Jani Nikula       2019-10-04  29  
63bf8301aac492 Jani Nikula       2019-10-04  30  	if (state == VGA_SWITCHEROO_ON) {
f54efb6ad03322 Jani Nikula       2020-04-02  31  		drm_info(&i915->drm, "switched on\n");
63bf8301aac492 Jani Nikula       2019-10-04  32  		i915->drm.switch_power_state = DRM_SWITCH_POWER_CHANGING;
63bf8301aac492 Jani Nikula       2019-10-04  33  		/* i915 resume handler doesn't set to D0 */
63bf8301aac492 Jani Nikula       2019-10-04  34  		pci_set_power_state(pdev, PCI_D0);
b8d65b8a5aea33 Jani Nikula       2021-11-11  35  		i915_driver_resume_switcheroo(i915);
63bf8301aac492 Jani Nikula       2019-10-04  36  		i915->drm.switch_power_state = DRM_SWITCH_POWER_ON;
63bf8301aac492 Jani Nikula       2019-10-04  37  	} else {
f54efb6ad03322 Jani Nikula       2020-04-02  38  		drm_info(&i915->drm, "switched off\n");
63bf8301aac492 Jani Nikula       2019-10-04  39  		i915->drm.switch_power_state = DRM_SWITCH_POWER_CHANGING;
b8d65b8a5aea33 Jani Nikula       2021-11-11  40  		i915_driver_suspend_switcheroo(i915, pmm);
63bf8301aac492 Jani Nikula       2019-10-04  41  		i915->drm.switch_power_state = DRM_SWITCH_POWER_OFF;
63bf8301aac492 Jani Nikula       2019-10-04  42  	}
63bf8301aac492 Jani Nikula       2019-10-04  43  }
63bf8301aac492 Jani Nikula       2019-10-04  44  
63bf8301aac492 Jani Nikula       2019-10-04  45  static bool i915_switcheroo_can_switch(struct pci_dev *pdev)
63bf8301aac492 Jani Nikula       2019-10-04  46  {
63bf8301aac492 Jani Nikula       2019-10-04  47  	struct drm_i915_private *i915 = pdev_to_i915(pdev);
d2e184f8e16ab8 Jani Nikula       2025-08-06 @48  	struct intel_display *display = i915->display;
63bf8301aac492 Jani Nikula       2019-10-04  49  
63bf8301aac492 Jani Nikula       2019-10-04  50  	/*
63bf8301aac492 Jani Nikula       2019-10-04  51  	 * FIXME: open_count is protected by drm_global_mutex but that would lead to
63bf8301aac492 Jani Nikula       2019-10-04  52  	 * locking inversion with the driver load path. And the access here is
63bf8301aac492 Jani Nikula       2019-10-04  53  	 * completely racy anyway. So don't bother with locking for now.
63bf8301aac492 Jani Nikula       2019-10-04  54  	 */
d2e184f8e16ab8 Jani Nikula       2025-08-06 @55  	return i915 && HAS_DISPLAY(display) && atomic_read(&i915->drm.open_count) == 0;
63bf8301aac492 Jani Nikula       2019-10-04  56  }
63bf8301aac492 Jani Nikula       2019-10-04  57  

:::::: The code at line 21 was first introduced by commit
:::::: 63bf8301aac492d4c5fdf7b0ec42b142c05080e3 drm/i915: split out i915_switcheroo.[ch] from i915_drv.c

:::::: TO: Jani Nikula <jani.nikula@intel.com>
:::::: CC: Jani Nikula <jani.nikula@intel.com>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

^ permalink raw reply	[flat|nested] 5+ messages in thread

* [drm-i915:for-linux-next 11/18] drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)
@ 2025-08-15 20:09 ` Dan Carpenter
  0 siblings, 0 replies; 5+ messages in thread
From: Dan Carpenter @ 2025-08-15 20:09 UTC (permalink / raw)
  To: oe-kbuild, Jani Nikula; +Cc: lkp, oe-kbuild-all, Gustavo Sousa

tree:   https://gitlab.freedesktop.org/drm/i915/kernel for-linux-next
head:   63e0b17ae79a4365e874d7e2ff3816db2e6d55b5
commit: d2e184f8e16ab85876ddcc0779358fbfe5162414 [11/18] drm/i915/switcheroo: pass display to HAS_DISPLAY()
config: i386-randconfig-141-20250815 (https://download.01.org/0day-ci/archive/20250816/202508160035.hmzuKiww-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202508160035.hmzuKiww-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)
drivers/gpu/drm/i915/i915_switcheroo.c:55 i915_switcheroo_can_switch() warn: variable dereferenced before check 'i915' (see line 48)

vim +/i915 +21 drivers/gpu/drm/i915/i915_switcheroo.c

63bf8301aac492 Jani Nikula       2019-10-04  14  static void i915_switcheroo_set_state(struct pci_dev *pdev,
63bf8301aac492 Jani Nikula       2019-10-04  15  				      enum vga_switcheroo_state state)
63bf8301aac492 Jani Nikula       2019-10-04  16  {
63bf8301aac492 Jani Nikula       2019-10-04  17  	struct drm_i915_private *i915 = pdev_to_i915(pdev);
d2e184f8e16ab8 Jani Nikula       2025-08-06 @18  	struct intel_display *display = i915->display;
                                                                                        ^^^^^^^^^^^^^
Patch adds a dereference

63bf8301aac492 Jani Nikula       2019-10-04  19  	pm_message_t pmm = { .event = PM_EVENT_SUSPEND };
63bf8301aac492 Jani Nikula       2019-10-04  20  
63bf8301aac492 Jani Nikula       2019-10-04 @21  	if (!i915) {
                                                            ^^^^^
Checked too late.

63bf8301aac492 Jani Nikula       2019-10-04  22  		dev_err(&pdev->dev, "DRM not initialized, aborting switch.\n");
63bf8301aac492 Jani Nikula       2019-10-04  23  		return;
63bf8301aac492 Jani Nikula       2019-10-04  24  	}
d2e184f8e16ab8 Jani Nikula       2025-08-06  25  	if (!HAS_DISPLAY(display)) {
a273e95721e968 Thomas Zimmermann 2023-01-16  26  		dev_err(&pdev->dev, "Device state not initialized, aborting switch.\n");
a273e95721e968 Thomas Zimmermann 2023-01-16  27  		return;
a273e95721e968 Thomas Zimmermann 2023-01-16  28  	}
63bf8301aac492 Jani Nikula       2019-10-04  29  
63bf8301aac492 Jani Nikula       2019-10-04  30  	if (state == VGA_SWITCHEROO_ON) {
f54efb6ad03322 Jani Nikula       2020-04-02  31  		drm_info(&i915->drm, "switched on\n");
63bf8301aac492 Jani Nikula       2019-10-04  32  		i915->drm.switch_power_state = DRM_SWITCH_POWER_CHANGING;
63bf8301aac492 Jani Nikula       2019-10-04  33  		/* i915 resume handler doesn't set to D0 */
63bf8301aac492 Jani Nikula       2019-10-04  34  		pci_set_power_state(pdev, PCI_D0);
b8d65b8a5aea33 Jani Nikula       2021-11-11  35  		i915_driver_resume_switcheroo(i915);
63bf8301aac492 Jani Nikula       2019-10-04  36  		i915->drm.switch_power_state = DRM_SWITCH_POWER_ON;
63bf8301aac492 Jani Nikula       2019-10-04  37  	} else {
f54efb6ad03322 Jani Nikula       2020-04-02  38  		drm_info(&i915->drm, "switched off\n");
63bf8301aac492 Jani Nikula       2019-10-04  39  		i915->drm.switch_power_state = DRM_SWITCH_POWER_CHANGING;
b8d65b8a5aea33 Jani Nikula       2021-11-11  40  		i915_driver_suspend_switcheroo(i915, pmm);
63bf8301aac492 Jani Nikula       2019-10-04  41  		i915->drm.switch_power_state = DRM_SWITCH_POWER_OFF;
63bf8301aac492 Jani Nikula       2019-10-04  42  	}
63bf8301aac492 Jani Nikula       2019-10-04  43  }
63bf8301aac492 Jani Nikula       2019-10-04  44  
63bf8301aac492 Jani Nikula       2019-10-04  45  static bool i915_switcheroo_can_switch(struct pci_dev *pdev)
63bf8301aac492 Jani Nikula       2019-10-04  46  {
63bf8301aac492 Jani Nikula       2019-10-04  47  	struct drm_i915_private *i915 = pdev_to_i915(pdev);
d2e184f8e16ab8 Jani Nikula       2025-08-06 @48  	struct intel_display *display = i915->display;
                                                                                        ^^^^^^^^^^^^^
Dereference

63bf8301aac492 Jani Nikula       2019-10-04  49  
63bf8301aac492 Jani Nikula       2019-10-04  50  	/*
63bf8301aac492 Jani Nikula       2019-10-04  51  	 * FIXME: open_count is protected by drm_global_mutex but that would lead to
63bf8301aac492 Jani Nikula       2019-10-04  52  	 * locking inversion with the driver load path. And the access here is
63bf8301aac492 Jani Nikula       2019-10-04  53  	 * completely racy anyway. So don't bother with locking for now.
63bf8301aac492 Jani Nikula       2019-10-04  54  	 */
d2e184f8e16ab8 Jani Nikula       2025-08-06 @55  	return i915 && HAS_DISPLAY(display) && atomic_read(&i915->drm.open_count) == 0;
                                                               ^^^^
The old code assumed that i915 could be NULL.

63bf8301aac492 Jani Nikula       2019-10-04  56  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [drm-i915:for-linux-next 11/18] drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)
  2025-08-15 20:09 ` Dan Carpenter
  (?)
@ 2025-08-18  7:18 ` Jani Nikula
  2025-08-18  8:07   ` Dan Carpenter
  -1 siblings, 1 reply; 5+ messages in thread
From: Jani Nikula @ 2025-08-18  7:18 UTC (permalink / raw)
  To: Dan Carpenter, oe-kbuild; +Cc: lkp, oe-kbuild-all, Gustavo Sousa

On Fri, 15 Aug 2025, Dan Carpenter <dan.carpenter@linaro.org> wrote:
> tree:   https://gitlab.freedesktop.org/drm/i915/kernel for-linux-next
> head:   63e0b17ae79a4365e874d7e2ff3816db2e6d55b5
> commit: d2e184f8e16ab85876ddcc0779358fbfe5162414 [11/18] drm/i915/switcheroo: pass display to HAS_DISPLAY()
> config: i386-randconfig-141-20250815 (https://download.01.org/0day-ci/archive/20250816/202508160035.hmzuKiww-lkp@intel.com/config)
> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> | Closes: https://lore.kernel.org/r/202508160035.hmzuKiww-lkp@intel.com/

Side note, this triplet of tags leads to checkpatch warning:

WARNING:BAD_REPORTED_BY_LINK: Reported-by: should be immediately
followed by Closes: with a URL to the report

> smatch warnings:
> drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)
> drivers/gpu/drm/i915/i915_switcheroo.c:55 i915_switcheroo_can_switch() warn: variable dereferenced before check 'i915' (see line 48)

Thanks for the report, fix at [1].

BR,
Jani.


[1] https://lore.kernel.org/r/20250818071605.2541523-1-jani.nikula@intel.com


-- 
Jani Nikula, Intel

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [drm-i915:for-linux-next 11/18] drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)
  2025-08-18  7:18 ` Jani Nikula
@ 2025-08-18  8:07   ` Dan Carpenter
  2025-08-18 11:57     ` Jani Nikula
  0 siblings, 1 reply; 5+ messages in thread
From: Dan Carpenter @ 2025-08-18  8:07 UTC (permalink / raw)
  To: Jani Nikula; +Cc: oe-kbuild, lkp, oe-kbuild-all, Gustavo Sousa

On Mon, Aug 18, 2025 at 10:18:14AM +0300, Jani Nikula wrote:
> On Fri, 15 Aug 2025, Dan Carpenter <dan.carpenter@linaro.org> wrote:
> > tree:   https://gitlab.freedesktop.org/drm/i915/kernel for-linux-next
> > head:   63e0b17ae79a4365e874d7e2ff3816db2e6d55b5
> > commit: d2e184f8e16ab85876ddcc0779358fbfe5162414 [11/18] drm/i915/switcheroo: pass display to HAS_DISPLAY()
> > config: i386-randconfig-141-20250815 (https://download.01.org/0day-ci/archive/20250816/202508160035.hmzuKiww-lkp@intel.com/config)
> > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > | Closes: https://lore.kernel.org/r/202508160035.hmzuKiww-lkp@intel.com/
> 
> Side note, this triplet of tags leads to checkpatch warning:
> 
> WARNING:BAD_REPORTED_BY_LINK: Reported-by: should be immediately
> followed by Closes: with a URL to the report
> 

It's hard to know what to do about that...  There is only one link but
both zero day and I rely on Reported-by tags to justify our saleries..

regards,
dan carpenter


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [drm-i915:for-linux-next 11/18] drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18)
  2025-08-18  8:07   ` Dan Carpenter
@ 2025-08-18 11:57     ` Jani Nikula
  0 siblings, 0 replies; 5+ messages in thread
From: Jani Nikula @ 2025-08-18 11:57 UTC (permalink / raw)
  To: Dan Carpenter; +Cc: oe-kbuild, lkp, oe-kbuild-all, Gustavo Sousa

On Mon, 18 Aug 2025, Dan Carpenter <dan.carpenter@linaro.org> wrote:
> On Mon, Aug 18, 2025 at 10:18:14AM +0300, Jani Nikula wrote:
>> On Fri, 15 Aug 2025, Dan Carpenter <dan.carpenter@linaro.org> wrote:
>> > tree:   https://gitlab.freedesktop.org/drm/i915/kernel for-linux-next
>> > head:   63e0b17ae79a4365e874d7e2ff3816db2e6d55b5
>> > commit: d2e184f8e16ab85876ddcc0779358fbfe5162414 [11/18] drm/i915/switcheroo: pass display to HAS_DISPLAY()
>> > config: i386-randconfig-141-20250815 (https://download.01.org/0day-ci/archive/20250816/202508160035.hmzuKiww-lkp@intel.com/config)
>> > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
>> >
>> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
>> > the same patch/commit), kindly add following tags
>> > | Reported-by: kernel test robot <lkp@intel.com>
>> > | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
>> > | Closes: https://lore.kernel.org/r/202508160035.hmzuKiww-lkp@intel.com/
>> 
>> Side note, this triplet of tags leads to checkpatch warning:
>> 
>> WARNING:BAD_REPORTED_BY_LINK: Reported-by: should be immediately
>> followed by Closes: with a URL to the report
>> 
>
> It's hard to know what to do about that...  There is only one link but
> both zero day and I rely on Reported-by tags to justify our saleries..

Make checkpatch allow multiple reported by for one mail? *shrug*

BR,
Jani.

-- 
Jani Nikula, Intel

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2025-08-18 11:57 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-08-15 17:01 [drm-i915:for-linux-next 11/18] drivers/gpu/drm/i915/i915_switcheroo.c:21 i915_switcheroo_set_state() warn: variable dereferenced before check 'i915' (see line 18) kernel test robot
2025-08-15 20:09 ` Dan Carpenter
2025-08-18  7:18 ` Jani Nikula
2025-08-18  8:07   ` Dan Carpenter
2025-08-18 11:57     ` Jani Nikula

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