[PATCH] drm/i915: add sanity check for partial view creation

[Matthew Auld <matthew.auld@intel.com>]

Upon creating a partial view we should check that the offset + size is
valid relative to the size of the gem object.

v2:
(Tvrtko Ursulin)
    - Don't use pages->nents to determine the page count
v3:
(Chris Wilson)
    - Handle potential overflow
v4:
(Chris Wilson)
    - Idiomatically handle overflow
    - Less idiotic placement
    - Treat as programmer error

Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index fb0f963..593eb15 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3356,6 +3356,14 @@ i915_gem_obj_lookup_or_create_ggtt_vma(struct drm_i915_gem_object *obj,
 	if (WARN_ON(!view))
 		return ERR_PTR(-EINVAL);
 
+	if (view->type == I915_GGTT_VIEW_PARTIAL) {
+		unsigned int page_count = obj->base.size >> PAGE_SHIFT;
+		if (WARN_ON(view->params.partial.offset > page_count ||
+			    view->params.partial.size > page_count  -
+			    view->params.partial.offset))
+			return ERR_PTR(-EINVAL);
+	}
+
 	vma = i915_gem_obj_to_ggtt_view(obj, view);
 
 	if (IS_ERR(vma))
-- 
2.4.3

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