drm/i915: Use range_overflows()

Replace a few more open-coded overflow checks with the macro.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152013.24684-4-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_stolen.c

@@ -505,7 +505,7 @@ i915_pages_create_for_stolen(struct drm_device *dev,
 	struct sg_table *st;
 	struct scatterlist *sg;
 
-	GEM_BUG_ON(offset > dev_priv->ggtt.stolen_size - size);
+	GEM_BUG_ON(range_overflows(offset, size, dev_priv->ggtt.stolen_size));
 
 	/* We hide that we have no struct page backing our stolen object
 	 * by wrapping the contiguous physical allocation with a fake

drivers/gpu/drm/i915/i915_vma.c

@@ -403,7 +403,8 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 
 	if (flags & PIN_OFFSET_FIXED) {
 		u64 offset = flags & PIN_OFFSET_MASK;
-		if (offset & (alignment - 1) || offset > end - size) {
+		if (offset & (alignment - 1) ||
+		    range_overflows(offset, size, end)) {
 			ret = -EINVAL;
 			goto err_unpin;
 		}

drivers/gpu/drm/i915/intel_bios.c

@@ -1416,13 +1416,16 @@ bool intel_bios_is_valid_vbt(const void *buf, size_t size)
 		return false;
 	}
 
-	if (vbt->bdb_offset + sizeof(struct bdb_header) > size) {
+	if (range_overflows_t(size_t,
+			      vbt->bdb_offset,
+			      sizeof(struct bdb_header),
+			      size)) {
 		DRM_DEBUG_DRIVER("BDB header incomplete\n");
 		return false;
 	}
 
 	bdb = get_bdb_header(vbt);
-	if (vbt->bdb_offset + bdb->bdb_size > size) {
+	if (range_overflows_t(size_t, vbt->bdb_offset, bdb->bdb_size, size)) {
 		DRM_DEBUG_DRIVER("BDB incomplete\n");
 		return false;
 	}