[PATCH 1/2] drm/i915: Don't drop pinned fences

[Daniel Vetter <daniel.vetter@ffwll.ch>]

Userspace can currently provoke this when e.g. trying to use a pinned
scanout as a cursor or overlay target. Later on that might lead to
some fun fence pin count mayhem.

Spurred by Ville's report that something goes wrong here and
originally I've thought that this might slip through the pwrite gtt
fastpath. But that one checks of obj tiling, so should be ok.

But one thing that _does_ blow up is the vma unbinding with more than
one address space. The next patch will fix this.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/i915_gem.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 05e79fa02db2..9559d33cd94b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3058,6 +3058,9 @@ i915_gem_object_put_fence(struct drm_i915_gem_object *obj)
 
 	fence = &dev_priv->fence_regs[obj->fence_reg];
 
+	if (fence->pin_count)
+		return -EBUSY;
+
 	i915_gem_object_fence_lost(obj);
 	i915_gem_object_update_fence(obj, fence, false);
 
-- 
1.8.5.2

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