cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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object.c (1775B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Landlock LSM - Object management
      4 *
      5 * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
      6 * Copyright © 2018-2020 ANSSI
      7 */
      8
      9#include <linux/bug.h>
     10#include <linux/compiler_types.h>
     11#include <linux/err.h>
     12#include <linux/kernel.h>
     13#include <linux/rcupdate.h>
     14#include <linux/refcount.h>
     15#include <linux/slab.h>
     16#include <linux/spinlock.h>
     17
     18#include "object.h"
     19
     20struct landlock_object *
     21landlock_create_object(const struct landlock_object_underops *const underops,
     22		       void *const underobj)
     23{
     24	struct landlock_object *new_object;
     25
     26	if (WARN_ON_ONCE(!underops || !underobj))
     27		return ERR_PTR(-ENOENT);
     28	new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT);
     29	if (!new_object)
     30		return ERR_PTR(-ENOMEM);
     31	refcount_set(&new_object->usage, 1);
     32	spin_lock_init(&new_object->lock);
     33	new_object->underops = underops;
     34	new_object->underobj = underobj;
     35	return new_object;
     36}
     37
     38/*
     39 * The caller must own the object (i.e. thanks to object->usage) to safely put
     40 * it.
     41 */
     42void landlock_put_object(struct landlock_object *const object)
     43{
     44	/*
     45	 * The call to @object->underops->release(object) might sleep, e.g.
     46	 * because of iput().
     47	 */
     48	might_sleep();
     49	if (!object)
     50		return;
     51
     52	/*
     53	 * If the @object's refcount cannot drop to zero, we can just decrement
     54	 * the refcount without holding a lock. Otherwise, the decrement must
     55	 * happen under @object->lock for synchronization with things like
     56	 * get_inode_object().
     57	 */
     58	if (refcount_dec_and_lock(&object->usage, &object->lock)) {
     59		__acquire(&object->lock);
     60		/*
     61		 * With @object->lock initially held, remove the reference from
     62		 * @object->underobj to @object (if it still exists).
     63		 */
     64		object->underops->release(object);
     65		kfree_rcu(object, rcu_free);
     66	}
     67}