1 /* 2 * linux/ipc/namespace.c 3 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc. 4 */ 5 6 #include <linux/ipc.h> 7 #include <linux/msg.h> 8 #include <linux/ipc_namespace.h> 9 #include <linux/rcupdate.h> 10 #include <linux/nsproxy.h> 11 #include <linux/slab.h> 12 #include <linux/fs.h> 13 #include <linux/mount.h> 14 #include <linux/user_namespace.h> 15 #include <linux/proc_fs.h> 16 17 #include "util.h" 18 19 static struct ipc_namespace *create_ipc_ns(struct task_struct *tsk, 20 struct ipc_namespace *old_ns) 21 { 22 struct ipc_namespace *ns; 23 int err; 24 25 ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL); 26 if (ns == NULL) 27 return ERR_PTR(-ENOMEM); 28 29 atomic_set(&ns->count, 1); 30 err = mq_init_ns(ns); 31 if (err) { 32 kfree(ns); 33 return ERR_PTR(err); 34 } 35 atomic_inc(&nr_ipc_ns); 36 37 sem_init_ns(ns); 38 msg_init_ns(ns); 39 shm_init_ns(ns); 40 41 /* 42 * msgmni has already been computed for the new ipc ns. 43 * Thus, do the ipcns creation notification before registering that 44 * new ipcns in the chain. 45 */ 46 ipcns_notify(IPCNS_CREATED); 47 register_ipcns_notifier(ns); 48 49 ns->user_ns = get_user_ns(task_cred_xxx(tsk, user)->user_ns); 50 51 return ns; 52 } 53 54 struct ipc_namespace *copy_ipcs(unsigned long flags, 55 struct task_struct *tsk) 56 { 57 struct ipc_namespace *ns = tsk->nsproxy->ipc_ns; 58 59 if (!(flags & CLONE_NEWIPC)) 60 return get_ipc_ns(ns); 61 return create_ipc_ns(tsk, ns); 62 } 63 64 /* 65 * free_ipcs - free all ipcs of one type 66 * @ns: the namespace to remove the ipcs from 67 * @ids: the table of ipcs to free 68 * @free: the function called to free each individual ipc 69 * 70 * Called for each kind of ipc when an ipc_namespace exits. 71 */ 72 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, 73 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) 74 { 75 struct kern_ipc_perm *perm; 76 int next_id; 77 int total, in_use; 78 79 down_write(&ids->rw_mutex); 80 81 in_use = ids->in_use; 82 83 for (total = 0, next_id = 0; total < in_use; next_id++) { 84 perm = idr_find(&ids->ipcs_idr, next_id); 85 if (perm == NULL) 86 continue; 87 ipc_lock_by_ptr(perm); 88 free(ns, perm); 89 total++; 90 } 91 up_write(&ids->rw_mutex); 92 } 93 94 static void free_ipc_ns(struct ipc_namespace *ns) 95 { 96 /* 97 * Unregistering the hotplug notifier at the beginning guarantees 98 * that the ipc namespace won't be freed while we are inside the 99 * callback routine. Since the blocking_notifier_chain_XXX routines 100 * hold a rw lock on the notifier list, unregister_ipcns_notifier() 101 * won't take the rw lock before blocking_notifier_call_chain() has 102 * released the rd lock. 103 */ 104 unregister_ipcns_notifier(ns); 105 sem_exit_ns(ns); 106 msg_exit_ns(ns); 107 shm_exit_ns(ns); 108 atomic_dec(&nr_ipc_ns); 109 110 /* 111 * Do the ipcns removal notification after decrementing nr_ipc_ns in 112 * order to have a correct value when recomputing msgmni. 113 */ 114 ipcns_notify(IPCNS_REMOVED); 115 put_user_ns(ns->user_ns); 116 kfree(ns); 117 } 118 119 /* 120 * put_ipc_ns - drop a reference to an ipc namespace. 121 * @ns: the namespace to put 122 * 123 * If this is the last task in the namespace exiting, and 124 * it is dropping the refcount to 0, then it can race with 125 * a task in another ipc namespace but in a mounts namespace 126 * which has this ipcns's mqueuefs mounted, doing some action 127 * with one of the mqueuefs files. That can raise the refcount. 128 * So dropping the refcount, and raising the refcount when 129 * accessing it through the VFS, are protected with mq_lock. 130 * 131 * (Clearly, a task raising the refcount on its own ipc_ns 132 * needn't take mq_lock since it can't race with the last task 133 * in the ipcns exiting). 134 */ 135 void put_ipc_ns(struct ipc_namespace *ns) 136 { 137 if (atomic_dec_and_lock(&ns->count, &mq_lock)) { 138 mq_clear_sbinfo(ns); 139 spin_unlock(&mq_lock); 140 mq_put_mnt(ns); 141 free_ipc_ns(ns); 142 } 143 } 144 145 static void *ipcns_get(struct task_struct *task) 146 { 147 struct ipc_namespace *ns = NULL; 148 struct nsproxy *nsproxy; 149 150 rcu_read_lock(); 151 nsproxy = task_nsproxy(task); 152 if (nsproxy) 153 ns = get_ipc_ns(nsproxy->ipc_ns); 154 rcu_read_unlock(); 155 156 return ns; 157 } 158 159 static void ipcns_put(void *ns) 160 { 161 return put_ipc_ns(ns); 162 } 163 164 static int ipcns_install(struct nsproxy *nsproxy, void *ns) 165 { 166 /* Ditch state from the old ipc namespace */ 167 exit_sem(current); 168 put_ipc_ns(nsproxy->ipc_ns); 169 nsproxy->ipc_ns = get_ipc_ns(ns); 170 return 0; 171 } 172 173 const struct proc_ns_operations ipcns_operations = { 174 .name = "ipc", 175 .type = CLONE_NEWIPC, 176 .get = ipcns_get, 177 .put = ipcns_put, 178 .install = ipcns_install, 179 }; 180