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