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-rw-r--r--security/landlock/object.c67
1 files changed, 67 insertions, 0 deletions
diff --git a/security/landlock/object.c b/security/landlock/object.c
new file mode 100644
index 0000000000..1f50612f01
--- /dev/null
+++ b/security/landlock/object.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Object management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#include <linux/bug.h>
+#include <linux/compiler_types.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/rcupdate.h>
+#include <linux/refcount.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include "object.h"
+
+struct landlock_object *
+landlock_create_object(const struct landlock_object_underops *const underops,
+ void *const underobj)
+{
+ struct landlock_object *new_object;
+
+ if (WARN_ON_ONCE(!underops || !underobj))
+ return ERR_PTR(-ENOENT);
+ new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT);
+ if (!new_object)
+ return ERR_PTR(-ENOMEM);
+ refcount_set(&new_object->usage, 1);
+ spin_lock_init(&new_object->lock);
+ new_object->underops = underops;
+ new_object->underobj = underobj;
+ return new_object;
+}
+
+/*
+ * The caller must own the object (i.e. thanks to object->usage) to safely put
+ * it.
+ */
+void landlock_put_object(struct landlock_object *const object)
+{
+ /*
+ * The call to @object->underops->release(object) might sleep, e.g.
+ * because of iput().
+ */
+ might_sleep();
+ if (!object)
+ return;
+
+ /*
+ * If the @object's refcount cannot drop to zero, we can just decrement
+ * the refcount without holding a lock. Otherwise, the decrement must
+ * happen under @object->lock for synchronization with things like
+ * get_inode_object().
+ */
+ if (refcount_dec_and_lock(&object->usage, &object->lock)) {
+ __acquire(&object->lock);
+ /*
+ * With @object->lock initially held, remove the reference from
+ * @object->underobj to @object (if it still exists).
+ */
+ object->underops->release(object);
+ kfree_rcu(object, rcu_free);
+ }
+}