intel-agp: fix a panic with 1M of shared memory, no GTT entries

When GTT size is equal to amount of video memory, the amount of GTT entries is computed lower than zero, which is invalid and leads to off-by-one error in intel_i915_configure() Originally posted here: http://bugzilla.kernel.org/show_bug.cgi?id=12539 http://bugzilla.redhat.com/show_bug.cgi?id=445592 Signed-off-by: Lubomir Rintel <[email protected]> Cc: Lubomir Rintel <[email protected]> Cc: Dave Airlie <[email protected]> Reviewed-by: Eric Anholt <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
cbmeeks · Mar 10, 2009 · 9c1e8a4 · 9c1e8a4
1 parent 229cc58
commit 9c1e8a4
Showing 1 changed file with 5 additions and 3 deletions.
diff --git a/drivers/char/agp/intel-agp.c b/drivers/char/agp/intel-agp.c
@@ -633,13 +633,15 @@ static void intel_i830_init_gtt_entries(void)
 			break;
 		}
 	}
-	if (gtt_entries > 0)
+	if (gtt_entries > 0) {
 		dev_info(&agp_bridge->dev->dev, "detected %dK %s memory\n",
 		       gtt_entries / KB(1), local ? "local" : "stolen");
-	else
+		gtt_entries /= KB(4);
+	} else {
 		dev_info(&agp_bridge->dev->dev,
 		       "no pre-allocated video memory detected\n");
-	gtt_entries /= KB(4);
+		gtt_entries = 0;
+	}
 
 	intel_private.gtt_entries = gtt_entries;
 }