Re: [PATCH 4/7] drivers/gpu/drm: remove invalid reference to listiterator variable

[Julia Lawall]

On Sun, 8 Jul 2012, Paul Menzel wrote:

> Dear Julia,
>
>
> Am Sonntag, den 08.07.2012, 13:37 +0200 schrieb Julia Lawall:
> > From: Julia Lawall <Julia.Lawall@xxxxxxx>
> >
> > If list_for_each_entry, etc complete a traversal of the list, the iterator
> > variable ends up pointing to an address at an offset from the list head,
> > and not a meaningful structure.  Thus this value should not be used after
> > the end of the iterator.
> >
> > In the first two cases, a a break is added after the switch; the break in
>
> s,a a,a,

Thanks.

> > the switch would jump out of the switch, but not out of the complete
> > iteration.
> >
> > In the first case, the null test on connector is removed, because the
> > iterator variable of list_for_each_entry is never null.
> >
> > In the third case, entry->base.crtc.fb is not a meaningful value.  What
> > seems to be intended is crtc->fb, which gets the information from the last
> > element of the list.
>
> maybe three separate patches would have been better?

OK, I wasn't sure what would be best.  I'll send three patches now.

> > These problems were found using Coccinelle (http://coccinelle.lip6.fr/).
>
> I always liked your example Coccinelle code snippets. Could you add them
> again to your commit messages? That would be awesome!

Sure.  I didn't include it because there was a 0/7 message that has the 
complete semantic patch.

julia

> > Signed-off-by: Julia Lawall <Julia.Lawall@xxxxxxx>
> >
> > ---
> >  drivers/gpu/drm/gma500/mdfld_intel_display.c |    4 +---
> >  drivers/gpu/drm/gma500/oaktrail_crtc.c       |    1 +
> >  drivers/gpu/drm/vmwgfx/vmwgfx_ldu.c          |    2 +-
> >  3 files changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/gma500/mdfld_intel_display.c b/drivers/gpu/drm/gma500/mdfld_intel_display.c
> > index 3f3cd61..fc1ced0 100644
> > --- a/drivers/gpu/drm/gma500/mdfld_intel_display.c
> > +++ b/drivers/gpu/drm/gma500/mdfld_intel_display.c
> > @@ -755,9 +755,6 @@ static int mdfld_crtc_mode_set(struct drm_crtc *crtc,
> >  					sizeof(struct drm_display_mode));
> >
> >  	list_for_each_entry(connector, &mode_config->connector_list, head) {
> > -		if (!connector)
> > -			continue;
> > -
> >  		encoder = connector->encoder;
> >
> >  		if (!encoder)
> > @@ -779,6 +776,7 @@ static int mdfld_crtc_mode_set(struct drm_crtc *crtc,
> >  			is_hdmi = true;
> >  			break;
> >  		}
> > +		break;
> >  	}
> >
> >  	/* Disable the VGA plane that we never use */
> > diff --git a/drivers/gpu/drm/gma500/oaktrail_crtc.c b/drivers/gpu/drm/gma500/oaktrail_crtc.c
> > index f821c83..4b2172e 100644
> > --- a/drivers/gpu/drm/gma500/oaktrail_crtc.c
> > +++ b/drivers/gpu/drm/gma500/oaktrail_crtc.c
> > @@ -329,6 +329,7 @@ static int oaktrail_crtc_mode_set(struct drm_crtc *crtc,
> >  			is_mipi = true;
> >  			break;
> >  		}
> > +		break;
> >  	}
> >
> >  	/* Disable the VGA plane that we never use */
> > diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ldu.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ldu.c
> > index 070fb23..634611a 100644
> > --- a/drivers/gpu/drm/vmwgfx/vmwgfx_ldu.c
> > +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ldu.c
> > @@ -93,7 +93,7 @@ static int vmw_ldu_commit_list(struct vmw_private *dev_priv)
> >
> >  		if (crtc == NULL)
> >  			return 0;
> > -		fb = entry->base.crtc.fb;
> > +		fb = crtc->fb;
> >
> >  		return vmw_kms_write_svga(dev_priv, w, h, fb->pitches[0],
> >  					  fb->bits_per_pixel, fb->depth);
>
> Acked-by: Paul Menzel <paulepanter@xxxxxxxxxxxxxxxxxxxxx>
>
>
> Thanks,
>
> Paul
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