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