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