143 lines
3.6 KiB
C
143 lines
3.6 KiB
C
/*
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* linux/ipc/namespace.c
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* Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
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*/
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#include <linux/ipc.h>
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#include <linux/msg.h>
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#include <linux/ipc_namespace.h>
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#include <linux/rcupdate.h>
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#include <linux/nsproxy.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/user_namespace.h>
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#include "util.h"
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static struct ipc_namespace *create_ipc_ns(struct task_struct *tsk,
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struct ipc_namespace *old_ns)
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{
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struct ipc_namespace *ns;
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int err;
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ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
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if (ns == NULL)
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return ERR_PTR(-ENOMEM);
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atomic_set(&ns->count, 1);
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err = mq_init_ns(ns);
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if (err) {
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kfree(ns);
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return ERR_PTR(err);
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}
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atomic_inc(&nr_ipc_ns);
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sem_init_ns(ns);
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msg_init_ns(ns);
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shm_init_ns(ns);
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/*
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* msgmni has already been computed for the new ipc ns.
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* Thus, do the ipcns creation notification before registering that
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* new ipcns in the chain.
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*/
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ipcns_notify(IPCNS_CREATED);
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register_ipcns_notifier(ns);
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ns->user_ns = get_user_ns(task_cred_xxx(tsk, user)->user_ns);
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return ns;
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}
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struct ipc_namespace *copy_ipcs(unsigned long flags,
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struct task_struct *tsk)
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{
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struct ipc_namespace *ns = tsk->nsproxy->ipc_ns;
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if (!(flags & CLONE_NEWIPC))
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return get_ipc_ns(ns);
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return create_ipc_ns(tsk, ns);
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}
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/*
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* free_ipcs - free all ipcs of one type
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* @ns: the namespace to remove the ipcs from
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* @ids: the table of ipcs to free
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* @free: the function called to free each individual ipc
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*
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* Called for each kind of ipc when an ipc_namespace exits.
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*/
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void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
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void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
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{
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struct kern_ipc_perm *perm;
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int next_id;
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int total, in_use;
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down_write(&ids->rw_mutex);
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in_use = ids->in_use;
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for (total = 0, next_id = 0; total < in_use; next_id++) {
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perm = idr_find(&ids->ipcs_idr, next_id);
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if (perm == NULL)
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continue;
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ipc_lock_by_ptr(perm);
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free(ns, perm);
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total++;
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}
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up_write(&ids->rw_mutex);
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}
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static void free_ipc_ns(struct ipc_namespace *ns)
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{
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/*
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* Unregistering the hotplug notifier at the beginning guarantees
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* that the ipc namespace won't be freed while we are inside the
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* callback routine. Since the blocking_notifier_chain_XXX routines
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* hold a rw lock on the notifier list, unregister_ipcns_notifier()
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* won't take the rw lock before blocking_notifier_call_chain() has
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* released the rd lock.
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*/
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unregister_ipcns_notifier(ns);
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sem_exit_ns(ns);
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msg_exit_ns(ns);
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shm_exit_ns(ns);
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atomic_dec(&nr_ipc_ns);
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/*
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* Do the ipcns removal notification after decrementing nr_ipc_ns in
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* order to have a correct value when recomputing msgmni.
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*/
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ipcns_notify(IPCNS_REMOVED);
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put_user_ns(ns->user_ns);
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kfree(ns);
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}
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/*
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* put_ipc_ns - drop a reference to an ipc namespace.
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* @ns: the namespace to put
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*
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* If this is the last task in the namespace exiting, and
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* it is dropping the refcount to 0, then it can race with
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* a task in another ipc namespace but in a mounts namespace
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* which has this ipcns's mqueuefs mounted, doing some action
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* with one of the mqueuefs files. That can raise the refcount.
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* So dropping the refcount, and raising the refcount when
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* accessing it through the VFS, are protected with mq_lock.
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*
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* (Clearly, a task raising the refcount on its own ipc_ns
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* needn't take mq_lock since it can't race with the last task
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* in the ipcns exiting).
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*/
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void put_ipc_ns(struct ipc_namespace *ns)
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{
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if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
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mq_clear_sbinfo(ns);
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spin_unlock(&mq_lock);
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mq_put_mnt(ns);
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free_ipc_ns(ns);
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}
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}
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