[PATCH 1/1] drm/i915: gracefully reject mmap of huge tiled objects

[James Xiong <james.xiong@intel.com>]

From: "Xiong, James" <james.xiong@intel.com>

currently mmap of a tiled object that is larger than mappable
aperture is rejected in fault handler, and causes sigbus error
and application crash.

This commit rejects it in mmap instead so that the client has
chance to handle the failure.

Signed-off-by: Xiong, James <james.xiong@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c |  2 +-
 drivers/gpu/drm/i915/i915_drv.h |  1 +
 drivers/gpu/drm/i915/i915_gem.c | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 0b9105cf3..c560406 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1808,7 +1808,7 @@ static const struct file_operations i915_driver_fops = {
 	.open = drm_open,
 	.release = drm_release,
 	.unlocked_ioctl = drm_ioctl,
-	.mmap = drm_gem_mmap,
+	.mmap = i915_gem_mmap,
 	.poll = drm_poll,
 	.read = drm_read,
 #ifdef CONFIG_COMPAT
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2e56e97..5867c3a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3062,6 +3062,7 @@ void *i915_gem_object_alloc(struct drm_device *dev);
 void i915_gem_object_free(struct drm_i915_gem_object *obj);
 void i915_gem_object_init(struct drm_i915_gem_object *obj,
 			 const struct drm_i915_gem_object_ops *ops);
+int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma);
 struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
 						  size_t size);
 struct drm_i915_gem_object *i915_gem_object_create_from_data(
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index aa4b63b..ce2e09f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5986,3 +5986,35 @@ fail:
 	drm_gem_object_unreference(&obj->base);
 	return ERR_PTR(ret);
 }
+
+int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct drm_file *priv = filp->private_data;
+	struct drm_device *dev = priv->minor->dev;
+	struct drm_gem_object *obj = NULL;
+	struct drm_vma_offset_node *node;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	drm_vma_offset_lock_lookup(dev->vma_offset_manager);
+	node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
+						vma->vm_pgoff,
+						vma_pages(vma));
+	if (likely(node)) {
+		obj = container_of(node, struct drm_gem_object, vma_node);
+		if (!kref_get_unless_zero(&obj->refcount))
+			obj = NULL;
+	}
+	drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
+
+	if (!obj)
+		return -EINVAL;
+
+	if (obj->size >= dev_priv->ggtt.mappable_end &&
+	    to_intel_bo(obj)->tiling_mode != I915_TILING_NONE) {
+		drm_gem_object_unreference_unlocked(obj);
+		return -ENOSPC;
+	}
+
+	drm_gem_object_unreference_unlocked(obj);
+	return drm_gem_mmap(filp, vma);
+}
-- 
1.9.1

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