drm/i915: Only fence tiled region of object.

When creating a fence for a tiled object, only fence the area that
makes up the actual tiles.  The object may be larger than the tiled
area and if we allow those extra addresses to be fenced, they'll
get converted to addresses beyond where the object is mapped. This
opens up the possiblity of writes beyond the end of object.

To prevent this, we adjust the size of the fence to only encompass
the area that makes up the actual tiles.  The extra space is considered
un-tiled and now behaves as if it was a linear object.

Testcase: igt/gem_tiled_fence_overflow
Reported-by: Dan Hettena <danh@ghs.com>
Signed-off-by: Bob Paauwe <bob.j.paauwe@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b4a4f36d2f00a43eb9f266c41a1a89b7e04903cf..5f614828d365555f70005aff470117ab15b3ae12 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3148,6 +3148,13 @@ static void i965_write_fence_reg(struct drm_device *dev, int reg,
                u32 size = i915_gem_obj_ggtt_size(obj);
                uint64_t val;
 
+               /* Adjust fence size to match tiled area */
+               if (obj->tiling_mode != I915_TILING_NONE) {
+                       uint32_t row_size = obj->stride *
+                               (obj->tiling_mode == I915_TILING_Y ? 32 : 8);
+                       size = (size / row_size) * row_size;
+               }
+
                val = (uint64_t)((i915_gem_obj_ggtt_offset(obj) + size - 4096) &
                                 0xfffff000) << 32;
                val |= i915_gem_obj_ggtt_offset(obj) & 0xfffff000;