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![Paul Mundt](/assets/img/avatar_default.png)
Slab destructors were no longer supported after Christoph's
c59def9f22
change. They've been
BUGs for both slab and slub, and slob never supported them
either.
This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
224 lines
5.4 KiB
C
224 lines
5.4 KiB
C
/*
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* The "user cache".
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*
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* (C) Copyright 1991-2000 Linus Torvalds
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*
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* We have a per-user structure to keep track of how many
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* processes, files etc the user has claimed, in order to be
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* able to have per-user limits for system resources.
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*/
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/bitops.h>
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#include <linux/key.h>
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#include <linux/interrupt.h>
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#include <linux/module.h>
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#include <linux/user_namespace.h>
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/*
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* UID task count cache, to get fast user lookup in "alloc_uid"
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* when changing user ID's (ie setuid() and friends).
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*/
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#define UIDHASH_MASK (UIDHASH_SZ - 1)
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#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
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#define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
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static struct kmem_cache *uid_cachep;
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/*
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* The uidhash_lock is mostly taken from process context, but it is
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* occasionally also taken from softirq/tasklet context, when
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* task-structs get RCU-freed. Hence all locking must be softirq-safe.
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* But free_uid() is also called with local interrupts disabled, and running
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* local_bh_enable() with local interrupts disabled is an error - we'll run
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* softirq callbacks, and they can unconditionally enable interrupts, and
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* the caller of free_uid() didn't expect that..
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*/
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static DEFINE_SPINLOCK(uidhash_lock);
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struct user_struct root_user = {
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.__count = ATOMIC_INIT(1),
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.processes = ATOMIC_INIT(1),
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.files = ATOMIC_INIT(0),
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.sigpending = ATOMIC_INIT(0),
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.mq_bytes = 0,
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.locked_shm = 0,
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#ifdef CONFIG_KEYS
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.uid_keyring = &root_user_keyring,
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.session_keyring = &root_session_keyring,
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#endif
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};
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/*
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* These routines must be called with the uidhash spinlock held!
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*/
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static inline void uid_hash_insert(struct user_struct *up, struct list_head *hashent)
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{
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list_add(&up->uidhash_list, hashent);
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}
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static inline void uid_hash_remove(struct user_struct *up)
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{
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list_del(&up->uidhash_list);
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}
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static inline struct user_struct *uid_hash_find(uid_t uid, struct list_head *hashent)
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{
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struct list_head *up;
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list_for_each(up, hashent) {
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struct user_struct *user;
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user = list_entry(up, struct user_struct, uidhash_list);
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if(user->uid == uid) {
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atomic_inc(&user->__count);
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return user;
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}
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}
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return NULL;
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}
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/*
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* Locate the user_struct for the passed UID. If found, take a ref on it. The
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* caller must undo that ref with free_uid().
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*
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* If the user_struct could not be found, return NULL.
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*/
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struct user_struct *find_user(uid_t uid)
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{
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struct user_struct *ret;
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unsigned long flags;
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struct user_namespace *ns = current->nsproxy->user_ns;
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spin_lock_irqsave(&uidhash_lock, flags);
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ret = uid_hash_find(uid, uidhashentry(ns, uid));
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spin_unlock_irqrestore(&uidhash_lock, flags);
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return ret;
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}
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void free_uid(struct user_struct *up)
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{
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unsigned long flags;
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if (!up)
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return;
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local_irq_save(flags);
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if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
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uid_hash_remove(up);
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spin_unlock_irqrestore(&uidhash_lock, flags);
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key_put(up->uid_keyring);
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key_put(up->session_keyring);
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kmem_cache_free(uid_cachep, up);
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} else {
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local_irq_restore(flags);
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}
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}
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struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
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{
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struct list_head *hashent = uidhashentry(ns, uid);
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struct user_struct *up;
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spin_lock_irq(&uidhash_lock);
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up = uid_hash_find(uid, hashent);
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spin_unlock_irq(&uidhash_lock);
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if (!up) {
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struct user_struct *new;
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new = kmem_cache_alloc(uid_cachep, GFP_KERNEL);
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if (!new)
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return NULL;
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new->uid = uid;
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atomic_set(&new->__count, 1);
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atomic_set(&new->processes, 0);
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atomic_set(&new->files, 0);
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atomic_set(&new->sigpending, 0);
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#ifdef CONFIG_INOTIFY_USER
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atomic_set(&new->inotify_watches, 0);
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atomic_set(&new->inotify_devs, 0);
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#endif
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new->mq_bytes = 0;
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new->locked_shm = 0;
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if (alloc_uid_keyring(new, current) < 0) {
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kmem_cache_free(uid_cachep, new);
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return NULL;
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}
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/*
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* Before adding this, check whether we raced
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* on adding the same user already..
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*/
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spin_lock_irq(&uidhash_lock);
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up = uid_hash_find(uid, hashent);
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if (up) {
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key_put(new->uid_keyring);
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key_put(new->session_keyring);
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kmem_cache_free(uid_cachep, new);
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} else {
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uid_hash_insert(new, hashent);
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up = new;
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}
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spin_unlock_irq(&uidhash_lock);
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}
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return up;
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}
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void switch_uid(struct user_struct *new_user)
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{
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struct user_struct *old_user;
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/* What if a process setreuid()'s and this brings the
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* new uid over his NPROC rlimit? We can check this now
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* cheaply with the new uid cache, so if it matters
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* we should be checking for it. -DaveM
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*/
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old_user = current->user;
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atomic_inc(&new_user->processes);
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atomic_dec(&old_user->processes);
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switch_uid_keyring(new_user);
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current->user = new_user;
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/*
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* We need to synchronize with __sigqueue_alloc()
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* doing a get_uid(p->user).. If that saw the old
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* user value, we need to wait until it has exited
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* its critical region before we can free the old
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* structure.
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*/
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smp_mb();
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spin_unlock_wait(¤t->sighand->siglock);
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free_uid(old_user);
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suid_keys(current);
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}
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static int __init uid_cache_init(void)
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{
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int n;
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uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
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0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
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for(n = 0; n < UIDHASH_SZ; ++n)
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INIT_LIST_HEAD(init_user_ns.uidhash_table + n);
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/* Insert the root user immediately (init already runs as root) */
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spin_lock_irq(&uidhash_lock);
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uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
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spin_unlock_irq(&uidhash_lock);
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return 0;
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}
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module_init(uid_cache_init);
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