Commit message: drm/i915: fix integer overflow in i915_gem_do_execbuffer()

On 32-bit systems, a large args->num_cliprects from userspace via ioctl
may overflow the allocation size, leading to out-of-bounds access.

This vulnerability was introduced in commit 432e58ed ("drm/i915: Avoid
allocation for execbuffer object list").

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
CVE: CVE-2012-2384
CWE: CWE-189
Vulnerability description: Integer overflow in the i915_gem_do_execbuffer function in drivers/gpu/drm/i915/i915_gem_execbuffer.c in the Direct Rendering Manager (DRM) subsystem in the Linux kernel before 3.3.5 on 32-bit platforms allows local users to cause a denial of service (out-of-bounds write) or possibly have unspecified other impact via a crafted ioctl call.

Project: linux
File: i915_gem_execbuffer.c

eb_get_object(struct eb_objects *eb, unsigned long handle)
{
	struct hlist_head *head;
	struct hlist_node *node;
	struct drm_i915_gem_object *obj;

	head = &eb->buckets[handle & eb->and];
	hlist_for_each(node, head) {
		obj = hlist_entry(node, struct drm_i915_gem_object, exec_node);
		if (obj->exec_handle == handle)
			return obj;
	}

	return NULL;
}

Project: linux
File: i915_gem_execbuffer.c

i915_gem_execbuffer_relocate_entry(struct drm_i915_gem_object *obj,
				   struct eb_objects *eb,
				   struct drm_i915_gem_relocation_entry *reloc)
{
	struct drm_device *dev = obj->base.dev;
	struct drm_gem_object *target_obj;
	uint32_t target_offset;
	int ret = -EINVAL;

	/* we've already hold a reference to all valid objects */
	target_obj = &eb_get_object(eb, reloc->target_handle)->base;
	if (unlikely(target_obj == NULL))
		return -ENOENT;

	target_offset = to_intel_bo(target_obj)->gtt_offset;

	/* The target buffer should have appeared before us in the
	 * exec_object list, so it should have a GTT space bound by now.
	 */
	if (unlikely(target_offset == 0)) {
		DRM_DEBUG("No GTT space found for object %d\n",
			  reloc->target_handle);
		return ret;
	}

	/* Validate that the target is in a valid r/w GPU domain */
	if (unlikely(reloc->write_domain & (reloc->write_domain - 1))) {
		DRM_DEBUG("reloc with multiple write domains: "
			  "obj %p target %d offset %d "
			  "read %08x write %08x",
			  obj, reloc->target_handle,
			  (int) reloc->offset,
			  reloc->read_domains,
			  reloc->write_domain);
		return ret;
	}
	if (unlikely((reloc->write_domain | reloc->read_domains)
		     & ~I915_GEM_GPU_DOMAINS)) {
		DRM_DEBUG("reloc with read/write non-GPU domains: "
			  "obj %p target %d offset %d "
			  "read %08x write %08x",
			  obj, reloc->target_handle,
			  (int) reloc->offset,
			  reloc->read_domains,
			  reloc->write_domain);
		return ret;
	}
	if (unlikely(reloc->write_domain && target_obj->pending_write_domain &&
		     reloc->write_domain != target_obj->pending_write_domain)) {
		DRM_DEBUG("Write domain conflict: "
			  "obj %p target %d offset %d "
			  "new %08x old %08x\n",
			  obj, reloc->target_handle,
			  (int) reloc->offset,
			  reloc->write_domain,
			  target_obj->pending_write_domain);
		return ret;
	}

	target_obj->pending_read_domains |= reloc->read_domains;
	target_obj->pending_write_domain |= reloc->write_domain;

	/* If the relocation already has the right value in it, no
	 * more work needs to be done.
	 */
	if (target_offset == reloc->presumed_offset)
		return 0;

	/* Check that the relocation address is valid... */
	if (unlikely(reloc->offset > obj->base.size - 4)) {
		DRM_DEBUG("Relocation beyond object bounds: "
			  "obj %p target %d offset %d size %d.\n",
			  obj, reloc->target_handle,
			  (int) reloc->offset,
			  (int) obj->base.size);
		return ret;
	}
	if (unlikely(reloc->offset & 3)) {
		DRM_DEBUG("Relocation not 4-byte aligned: "
			  "obj %p target %d offset %d.\n",
			  obj, reloc->target_handle,
			  (int) reloc->offset);
		return ret;
	}

	reloc->delta += target_offset;
	if (obj->base.write_domain == I915_GEM_DOMAIN_CPU) {
		uint32_t page_offset = reloc->offset & ~PAGE_MASK;
		char *vaddr;

		vaddr = kmap_atomic(obj->pages[reloc->offset >> PAGE_SHIFT]);
		*(uint32_t *)(vaddr + page_offset) = reloc->delta;
		kunmap_atomic(vaddr);
	} else {
		struct drm_i915_private *dev_priv = dev->dev_private;
		uint32_t __iomem *reloc_entry;
		void __iomem *reloc_page;

		/* We can't wait for rendering with pagefaults disabled */
		if (obj->active && in_atomic())
			return -EFAULT;

		ret = i915_gem_object_set_to_gtt_domain(obj, 1);
		if (ret)
			return ret;

		/* Map the page containing the relocation we're going to perform.  */
		reloc->offset += obj->gtt_offset;
		reloc_page = io_mapping_map_atomic_wc(dev_priv->mm.gtt_mapping,
						      reloc->offset & PAGE_MASK);
		reloc_entry = (uint32_t __iomem *)
			(reloc_page + (reloc->offset & ~PAGE_MASK));
		iowrite32(reloc->delta, reloc_entry);
		io_mapping_unmap_atomic(reloc_page);
	}

	/* and update the user's relocation entry */
	reloc->presumed_offset = target_offset;

	return 0;
}

Project: linux
File: i915_gem_execbuffer.c

i915_gem_execbuffer_relocate_object(struct drm_i915_gem_object *obj,
				    struct eb_objects *eb)
{
	struct drm_i915_gem_relocation_entry __user *user_relocs;
	struct drm_i915_gem_exec_object2 *entry = obj->exec_entry;
	int i, ret;

	user_relocs = (void __user *)(uintptr_t)entry->relocs_ptr;
	for (i = 0; i < entry->relocation_count; i++) {
		struct drm_i915_gem_relocation_entry reloc;

		if (__copy_from_user_inatomic(&reloc,
					      user_relocs+i,
					      sizeof(reloc)))
			return -EFAULT;

		ret = i915_gem_execbuffer_relocate_entry(obj, eb, &reloc);
		if (ret)
			return ret;

		if (__copy_to_user_inatomic(&user_relocs[i].presumed_offset,
					    &reloc.presumed_offset,
					    sizeof(reloc.presumed_offset)))
			return -EFAULT;
	}

	return 0;
}

Project: linux
File: i915_gem_execbuffer.c

i915_gem_execbuffer_relocate_object_slow(struct drm_i915_gem_object *obj,
					 struct eb_objects *eb,
					 struct drm_i915_gem_relocation_entry *relocs)
{
	const struct drm_i915_gem_exec_object2 *entry = obj->exec_entry;
	int i, ret;

	for (i = 0; i < entry->relocation_count; i++) {
		ret = i915_gem_execbuffer_relocate_entry(obj, eb, &relocs[i]);
		if (ret)
			return ret;
	}

	return 0;
}

Project: linux
File: i915_gem_execbuffer.c

i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
				  struct drm_file *file,
				  struct intel_ring_buffer *ring,
				  struct list_head *objects,
				  struct eb_objects *eb,
				  struct drm_i915_gem_exec_object2 *exec,
				  int count)
{
	struct drm_i915_gem_relocation_entry *reloc;
	struct drm_i915_gem_object *obj;
	int *reloc_offset;
	int i, total, ret;

	/* We may process another execbuffer during the unlock... */
	while (!list_empty(objects)) {
		obj = list_first_entry(objects,
				       struct drm_i915_gem_object,
				       exec_list);
		list_del_init(&obj->exec_list);
		drm_gem_object_unreference(&obj->base);
	}

	mutex_unlock(&dev->struct_mutex);

	total = 0;
	for (i = 0; i < count; i++)
		total += exec[i].relocation_count;

	reloc_offset = drm_malloc_ab(count, sizeof(*reloc_offset));
	reloc = drm_malloc_ab(total, sizeof(*reloc));
	if (reloc == NULL || reloc_offset == NULL) {
		drm_free_large(reloc);
		drm_free_large(reloc_offset);
		mutex_lock(&dev->struct_mutex);
		return -ENOMEM;
	}

	total = 0;
	for (i = 0; i < count; i++) {
		struct drm_i915_gem_relocation_entry __user *user_relocs;

		user_relocs = (void __user *)(uintptr_t)exec[i].relocs_ptr;

		if (copy_from_user(reloc+total, user_relocs,
				   exec[i].relocation_count * sizeof(*reloc))) {
			ret = -EFAULT;
			mutex_lock(&dev->struct_mutex);
			goto err;
		}

		reloc_offset[i] = total;
		total += exec[i].relocation_count;
	}

	ret = i915_mutex_lock_interruptible(dev);
	if (ret) {
		mutex_lock(&dev->struct_mutex);
		goto err;
	}

	/* reacquire the objects */
	eb_reset(eb);
	for (i = 0; i < count; i++) {
		obj = to_intel_bo(drm_gem_object_lookup(dev, file,
							exec[i].handle));
		if (&obj->base == NULL) {
			DRM_DEBUG("Invalid object handle %d at index %d\n",
				   exec[i].handle, i);
			ret = -ENOENT;
			goto err;
		}

		list_add_tail(&obj->exec_list, objects);
		obj->exec_handle = exec[i].handle;
		obj->exec_entry = &exec[i];
		eb_add_object(eb, obj);
	}

	ret = i915_gem_execbuffer_reserve(ring, file, objects);
	if (ret)
		goto err;

	list_for_each_entry(obj, objects, exec_list) {
		int offset = obj->exec_entry - exec;
		ret = i915_gem_execbuffer_relocate_object_slow(obj, eb,
							       reloc + reloc_offset[offset]);
		if (ret)
			goto err;
	}

	/* Leave the user relocations as are, this is the painfully slow path,
	 * and we want to avoid the complication of dropping the lock whilst
	 * having buffers reserved in the aperture and so causing spurious
	 * ENOSPC for random operations.
	 */

err:
	drm_free_large(reloc);
	drm_free_large(reloc_offset);
	return ret;
}

Project: linux
File: i915_gem_execbuffer.c

pin_and_fence_object(struct drm_i915_gem_object *obj,
		     struct intel_ring_buffer *ring)
{
	struct drm_i915_gem_exec_object2 *entry = obj->exec_entry;
	bool has_fenced_gpu_access = INTEL_INFO(ring->dev)->gen < 4;
	bool need_fence, need_mappable;
	int ret;

	need_fence =
		has_fenced_gpu_access &&
		entry->flags & EXEC_OBJECT_NEEDS_FENCE &&
		obj->tiling_mode != I915_TILING_NONE;
	need_mappable =
		entry->relocation_count ? true : need_fence;

	ret = i915_gem_object_pin(obj, entry->alignment, need_mappable);
	if (ret)
		return ret;

	if (has_fenced_gpu_access) {
		if (entry->flags & EXEC_OBJECT_NEEDS_FENCE) {
			if (obj->tiling_mode) {
				ret = i915_gem_object_get_fence(obj, ring);
				if (ret)
					goto err_unpin;

				entry->flags |= __EXEC_OBJECT_HAS_FENCE;
				i915_gem_object_pin_fence(obj);
			} else {
				ret = i915_gem_object_put_fence(obj);
				if (ret)
					goto err_unpin;
			}
			obj->pending_fenced_gpu_access = true;
		}
	}

	entry->offset = obj->gtt_offset;
	return 0;

err_unpin:
	i915_gem_object_unpin(obj);
	return ret;
}