drm/ttm: ttm object security fixes for render nodes

When a client looks up a ttm object, don't look it up through the device hash
table, but rather from the file hash table. That makes sure that the client
has indeed put a reference on the object, or in gem terms, has opened
the object; either using prime or using the global "name".

To avoid a performance loss, make sure the file hash table entries can be
looked up from under an RCU lock, and as a consequence, replace the rwlock
with a spinlock, since we never need to take it in read mode only anymore.

Finally add a ttm object lookup function for the device hash table, that is
intended to be used when we put a ref object on a base object or, in  gem terms,
when we open the object.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/include/drm/ttm/ttm_object.h b/include/drm/ttm/ttm_object.h
index 58b029894eb..0097cc03034 100644
--- a/include/drm/ttm/ttm_object.h
+++ b/include/drm/ttm/ttm_object.h
@@ -190,14 +190,26 @@ extern int ttm_base_object_init(struct ttm_object_file *tfile,
  * @key: Hash key
  *
  * Looks up a struct ttm_base_object with the key @key.
- * Also verifies that the object is visible to the application, by
- * comparing the @tfile argument and checking the object shareable flag.
  */
 
 extern struct ttm_base_object *ttm_base_object_lookup(struct ttm_object_file
 						      *tfile, uint32_t key);
 
 /**
+ * ttm_base_object_lookup_for_ref
+ *
+ * @tdev: Pointer to a struct ttm_object_device.
+ * @key: Hash key
+ *
+ * Looks up a struct ttm_base_object with the key @key.
+ * This function should only be used when the struct tfile associated with the
+ * caller doesn't yet have a reference to the base object.
+ */
+
+extern struct ttm_base_object *
+ttm_base_object_lookup_for_ref(struct ttm_object_device *tdev, uint32_t key);
+
+/**
  * ttm_base_object_unref
  *
  * @p_base: Pointer to a pointer referencing a struct ttm_base_object.
@@ -218,6 +230,8 @@ extern void ttm_base_object_unref(struct ttm_base_object **p_base);
  * @existed: Upon completion, indicates that an identical reference object
  * already existed, and the refcount was upped on that object instead.
  *
+ * Checks that the base object is shareable and adds a ref object to it.
+ *
  * Adding a ref object to a base object is basically like referencing the
  * base object, but a user-space application holds the reference. When the
  * file corresponding to @tfile is closed, all its reference objects are