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From:   Jani Nikula <jani.nikula@intel.com>
To:     Dan Carpenter <dan.carpenter@oracle.com>, kbuild@01.org
Cc:     kbuild-all@01.org, linux-kernel@vger.kernel.org,
        Chris Wilson <chris@chris-wilson.co.uk>,
        intel-gfx@lists.freedesktop.org,
        Ville =?utf-8?B?U3lyasOkbMOk?= <ville.syrjala@linux.intel.com>
Subject: Re: drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color_plane' after use.
In-Reply-To: <20190914040858.GT20699@kadam>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
References: <20190914040858.GT20699@kadam>
Date:   Mon, 16 Sep 2019 10:31:35 +0300
Message-ID: <87lfuou27c.fsf@intel.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Sat, 14 Sep 2019, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> tree:   https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   a7f89616b7376495424f682b6086e0c391a89a1d
> commit: df0566a641f959108c152be748a0a58794280e0e drm/i915: move modesetting core code under display/
> date:   3 months ago
>
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> New smatch warnings:
> drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color_plane' after use.
> drivers/gpu/drm/i915/display/intel_display.c:16328 intel_sanitize_encoder() error: we previously assumed 'crtc' could be null (see line 16318)

Odd, what changed to provoke the warnings now? Or is the smatch test
new?

Anyway, Cc: Ville & intel-gfx.

BR,
Jani.


>
> git remote add linus https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux.git
> git remote update linus
> git checkout df0566a641f959108c152be748a0a58794280e0e
> vim +/color_plane +3934 drivers/gpu/drm/i915/display/intel_display.c
>
> b3cf5c06ca5001 drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2018-09-25  3926  
> df79cf44191029 drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2018-09-11  3927  u32 skl_plane_stride(const struct intel_plane_state *plane_state,
> 5d2a19507cb665 drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2018-09-07  3928  		     int color_plane)
> d21967740f4b7d drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2016-01-28  3929  {
> df79cf44191029 drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2018-09-11  3930  	const struct drm_framebuffer *fb = plane_state->base.fb;
> df79cf44191029 drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2018-09-11  3931  	unsigned int rotation = plane_state->base.rotation;
> 5d2a19507cb665 drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2018-09-07  3932  	u32 stride = plane_state->color_plane[color_plane].stride;
>                                                                                                                               ^^^^^^^^^^^
> Out of bounds read?
>
> 1b500535c513ac drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2017-03-07  3933  
> 5d2a19507cb665 drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2018-09-07 @3934  	if (color_plane >= fb->format->num_planes)
>                                                                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Tested too late.
>
> 1b500535c513ac drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2017-03-07  3935  		return 0;
> 1b500535c513ac drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2017-03-07  3936  
> b3cf5c06ca5001 drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2018-09-25  3937  	return stride / skl_plane_stride_mult(fb, color_plane, rotation);
> d21967740f4b7d drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2016-01-28  3938  }
> d21967740f4b7d drivers/gpu/drm/i915/intel_display.c Ville Syrjälä 2016-01-28  3939  
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

-- 
Jani Nikula, Intel Open Source Graphics Center