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 #ifndef _SECURITY_LANDLOCK_OBJECT_H 10 #define _SECURITY_LANDLOCK_OBJECT_H 11 12 #include <linux/compiler_types.h> 13 #include <linux/refcount.h> 14 #include <linux/spinlock.h> 15 16 struct landlock_object; 17 18 /** 19 * struct landlock_object_underops - Operations on an underlying object 20 */ 21 struct landlock_object_underops { 22 /** 23 * @release: Releases the underlying object (e.g. iput() for an inode). 24 */ 25 void (*release)(struct landlock_object *const object) 26 __releases(object->lock); 27 }; 28 29 /** 30 * struct landlock_object - Security blob tied to a kernel object 31 * 32 * The goal of this structure is to enable to tie a set of ephemeral access 33 * rights (pertaining to different domains) to a kernel object (e.g an inode) 34 * in a safe way. This implies to handle concurrent use and modification. 35 * 36 * The lifetime of a &struct landlock_object depends on the rules referring to 37 * it. 38 */ 39 struct landlock_object { 40 /** 41 * @usage: This counter is used to tie an object to the rules matching 42 * it or to keep it alive while adding a new rule. If this counter 43 * reaches zero, this struct must not be modified, but this counter can 44 * still be read from within an RCU read-side critical section. When 45 * adding a new rule to an object with a usage counter of zero, we must 46 * wait until the pointer to this object is set to NULL (or recycled). 47 */ 48 refcount_t usage; 49 /** 50 * @lock: Protects against concurrent modifications. This lock must be 51 * held from the time @usage drops to zero until any weak references 52 * from @underobj to this object have been cleaned up. 53 * 54 * Lock ordering: inode->i_lock nests inside this. 55 */ 56 spinlock_t lock; 57 /** 58 * @underobj: Used when cleaning up an object and to mark an object as 59 * tied to its underlying kernel structure. This pointer is protected 60 * by @lock. Cf. landlock_release_inodes() and release_inode(). 61 */ 62 void *underobj; 63 union { 64 /** 65 * @rcu_free: Enables lockless use of @usage, @lock and 66 * @underobj from within an RCU read-side critical section. 67 * @rcu_free and @underops are only used by 68 * landlock_put_object(). 69 */ 70 struct rcu_head rcu_free; 71 /** 72 * @underops: Enables landlock_put_object() to release the 73 * underlying object (e.g. inode). 74 */ 75 const struct landlock_object_underops *underops; 76 }; 77 }; 78 79 struct landlock_object *landlock_create_object( 80 const struct landlock_object_underops *const underops, 81 void *const underobj); 82 83 void landlock_put_object(struct landlock_object *const object); 84 85 static inline void landlock_get_object(struct landlock_object *const object) 86 { 87 if (object) 88 refcount_inc(&object->usage); 89 } 90 91 #endif /* _SECURITY_LANDLOCK_OBJECT_H */ 92