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67 lines
1.7 KiB
67 lines
1.7 KiB
// 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 <[email protected]> |
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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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