[Intel-gfx] [PATCH] drm/i915/gt: Validation rotated vma bounds are within the object

[Chris Wilson]

Quite understandably, we bug out when asked to find a page that doesn't
belong to the object. However, we should report the error back to the
user long before we attempt the out-of-bound access! In this case, it is
insufficient validation on the rotated vma, with the simplest/cheapest
point for us to insert a bound check when we are computing the rotated
page lookups.

Similarly, it might be wise to see if we can validate the user input
upon creating the rotated framebuffer.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/951
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Matthew Auld <matthew.auld at intel.com
---
 drivers/gpu/drm/i915/gt/intel_ggtt.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index 99189cdba8a9..59a60968a6da 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -1283,6 +1283,7 @@ static noinline struct sg_table *
 intel_rotate_pages(struct intel_rotation_info *rot_info,
 		   struct drm_i915_gem_object *obj)
 {
+	const unsigned long npages = obj->base.size >> PAGE_SHIFT;
 	unsigned int size = intel_rotation_info_size(rot_info);
 	struct sg_table *st;
 	struct scatterlist *sg;
@@ -1302,9 +1303,23 @@ intel_rotate_pages(struct intel_rotation_info *rot_info,
 	sg = st->sgl;
 
 	for (i = 0 ; i < ARRAY_SIZE(rot_info->plane); i++) {
-		sg = rotate_pages(obj, rot_info->plane[i].offset,
-				  rot_info->plane[i].width, rot_info->plane[i].height,
-				  rot_info->plane[i].stride, st, sg);
+		const struct intel_remapped_plane_info *plane =
+			&rot_info->plane[i];
+		unsigned long last;
+
+		last = plane->offset;
+		last += (plane->height - 1) * plane->stride;
+		last += plane->width - 1;
+		if (last >= npages) {
+			ret = -EINVAL;
+			goto err_sg_alloc;
+		}
+
+		sg = rotate_pages(obj,
+				  plane->offset,
+				  plane->width, plane->height,
+				  plane->stride,
+				  st, sg);
 	}
 
 	return st;
-- 
2.25.0.rc2