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 20 struct landlock_object *landlock_create_object( 21 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 */ 42 void 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 } 68