linux-kernel - [PATCH 4/7] drivers/gpu/drm: remove invalid reference to list iterator variable

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Date:	Sun,  8 Jul 2012 13:37:41 +0200
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	David Airlie <airlied@...ux.ie>
Cc:	kernel-janitors@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/7] drivers/gpu/drm: remove invalid reference to list iterator variable

From: Julia Lawall <Julia.Lawall@...6.fr>

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
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.

These problems were found using Coccinelle (http://coccinelle.lip6.fr/).

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

---
 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);

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