drm/i915: Fix leak of relocs along do_execbuffer error path

Following a gpu hang, we would leak the relocation buffer. So simply
earrange the error path to always free the relocation buffer.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_gem.c

@@ -3584,6 +3584,9 @@ i915_gem_put_relocs_to_user(struct drm_i915_gem_exec_object2 *exec_list,
 	uint32_t reloc_count = 0, i;
 	int ret = 0;
 
+	if (relocs == NULL)
+	    return 0;
+
 	for (i = 0; i < buffer_count; i++) {
 		struct drm_i915_gem_relocation_entry __user *user_relocs;
 		int unwritten;
@@ -3673,7 +3676,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	struct drm_gem_object *batch_obj;
 	struct drm_i915_gem_object *obj_priv;
 	struct drm_clip_rect *cliprects = NULL;
-	struct drm_i915_gem_relocation_entry *relocs;
+	struct drm_i915_gem_relocation_entry *relocs = NULL;
 	int ret = 0, ret2, i, pinned = 0;
 	uint64_t exec_offset;
 	uint32_t seqno, flush_domains, reloc_index;
@@ -3950,6 +3953,7 @@ err:
 
 	mutex_unlock(&dev->struct_mutex);
 
+pre_mutex_err:
 	/* Copy the updated relocations out regardless of current error
 	 * state.  Failure to update the relocs would mean that the next
 	 * time userland calls execbuf, it would do so with presumed offset
@@ -3964,7 +3968,6 @@ err:
 			ret = ret2;
 	}
 
-pre_mutex_err:
 	drm_free_large(object_list);
 	kfree(cliprects);