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-rw-r--r--security/landlock/object.h91
1 files changed, 91 insertions, 0 deletions
diff --git a/security/landlock/object.h b/security/landlock/object.h
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+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock LSM - Object management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#ifndef _SECURITY_LANDLOCK_OBJECT_H
+#define _SECURITY_LANDLOCK_OBJECT_H
+
+#include <linux/compiler_types.h>
+#include <linux/refcount.h>
+#include <linux/spinlock.h>
+
+struct landlock_object;
+
+/**
+ * struct landlock_object_underops - Operations on an underlying object
+ */
+struct landlock_object_underops {
+ /**
+ * @release: Releases the underlying object (e.g. iput() for an inode).
+ */
+ void (*release)(struct landlock_object *const object)
+ __releases(object->lock);
+};
+
+/**
+ * struct landlock_object - Security blob tied to a kernel object
+ *
+ * The goal of this structure is to enable to tie a set of ephemeral access
+ * rights (pertaining to different domains) to a kernel object (e.g an inode)
+ * in a safe way. This implies to handle concurrent use and modification.
+ *
+ * The lifetime of a &struct landlock_object depends on the rules referring to
+ * it.
+ */
+struct landlock_object {
+ /**
+ * @usage: This counter is used to tie an object to the rules matching
+ * it or to keep it alive while adding a new rule. If this counter
+ * reaches zero, this struct must not be modified, but this counter can
+ * still be read from within an RCU read-side critical section. When
+ * adding a new rule to an object with a usage counter of zero, we must
+ * wait until the pointer to this object is set to NULL (or recycled).
+ */
+ refcount_t usage;
+ /**
+ * @lock: Protects against concurrent modifications. This lock must be
+ * held from the time @usage drops to zero until any weak references
+ * from @underobj to this object have been cleaned up.
+ *
+ * Lock ordering: inode->i_lock nests inside this.
+ */
+ spinlock_t lock;
+ /**
+ * @underobj: Used when cleaning up an object and to mark an object as
+ * tied to its underlying kernel structure. This pointer is protected
+ * by @lock. Cf. landlock_release_inodes() and release_inode().
+ */
+ void *underobj;
+ union {
+ /**
+ * @rcu_free: Enables lockless use of @usage, @lock and
+ * @underobj from within an RCU read-side critical section.
+ * @rcu_free and @underops are only used by
+ * landlock_put_object().
+ */
+ struct rcu_head rcu_free;
+ /**
+ * @underops: Enables landlock_put_object() to release the
+ * underlying object (e.g. inode).
+ */
+ const struct landlock_object_underops *underops;
+ };
+};
+
+struct landlock_object *
+landlock_create_object(const struct landlock_object_underops *const underops,
+ void *const underobj);
+
+void landlock_put_object(struct landlock_object *const object);
+
+static inline void landlock_get_object(struct landlock_object *const object)
+{
+ if (object)
+ refcount_inc(&object->usage);
+}
+
+#endif /* _SECURITY_LANDLOCK_OBJECT_H */