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 user_namespace *user_ns, 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 err = proc_alloc_inum(&ns->proc_inum); 30 if (err) { 31 kfree(ns); 32 return ERR_PTR(err); 33 } 34 35 atomic_set(&ns->count, 1); 36 err = mq_init_ns(ns); 37 if (err) { 38 proc_free_inum(ns->proc_inum); 39 kfree(ns); 40 return ERR_PTR(err); 41 } 42 atomic_inc(&nr_ipc_ns); 43 44 sem_init_ns(ns); 45 msg_init_ns(ns); 46 shm_init_ns(ns); 47 48 /* 49 * msgmni has already been computed for the new ipc ns. 50 * Thus, do the ipcns creation notification before registering that 51 * new ipcns in the chain. 52 */ 53 ipcns_notify(IPCNS_CREATED); 54 register_ipcns_notifier(ns); 55 56 ns->user_ns = get_user_ns(user_ns); 57 58 return ns; 59 } 60 61 struct ipc_namespace *copy_ipcs(unsigned long flags, 62 struct user_namespace *user_ns, struct ipc_namespace *ns) 63 { 64 if (!(flags & CLONE_NEWIPC)) 65 return get_ipc_ns(ns); 66 return create_ipc_ns(user_ns, ns); 67 } 68 69 /* 70 * free_ipcs - free all ipcs of one type 71 * @ns: the namespace to remove the ipcs from 72 * @ids: the table of ipcs to free 73 * @free: the function called to free each individual ipc 74 * 75 * Called for each kind of ipc when an ipc_namespace exits. 76 */ 77 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, 78 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) 79 { 80 struct kern_ipc_perm *perm; 81 int next_id; 82 int total, in_use; 83 84 down_write(&ids->rw_mutex); 85 86 in_use = ids->in_use; 87 88 for (total = 0, next_id = 0; total < in_use; next_id++) { 89 perm = idr_find(&ids->ipcs_idr, next_id); 90 if (perm == NULL) 91 continue; 92 ipc_lock_by_ptr(perm); 93 free(ns, perm); 94 total++; 95 } 96 up_write(&ids->rw_mutex); 97 } 98 99 static void free_ipc_ns(struct ipc_namespace *ns) 100 { 101 /* 102 * Unregistering the hotplug notifier at the beginning guarantees 103 * that the ipc namespace won't be freed while we are inside the 104 * callback routine. Since the blocking_notifier_chain_XXX routines 105 * hold a rw lock on the notifier list, unregister_ipcns_notifier() 106 * won't take the rw lock before blocking_notifier_call_chain() has 107 * released the rd lock. 108 */ 109 unregister_ipcns_notifier(ns); 110 sem_exit_ns(ns); 111 msg_exit_ns(ns); 112 shm_exit_ns(ns); 113 atomic_dec(&nr_ipc_ns); 114 115 /* 116 * Do the ipcns removal notification after decrementing nr_ipc_ns in 117 * order to have a correct value when recomputing msgmni. 118 */ 119 ipcns_notify(IPCNS_REMOVED); 120 put_user_ns(ns->user_ns); 121 proc_free_inum(ns->proc_inum); 122 kfree(ns); 123 } 124 125 /* 126 * put_ipc_ns - drop a reference to an ipc namespace. 127 * @ns: the namespace to put 128 * 129 * If this is the last task in the namespace exiting, and 130 * it is dropping the refcount to 0, then it can race with 131 * a task in another ipc namespace but in a mounts namespace 132 * which has this ipcns's mqueuefs mounted, doing some action 133 * with one of the mqueuefs files. That can raise the refcount. 134 * So dropping the refcount, and raising the refcount when 135 * accessing it through the VFS, are protected with mq_lock. 136 * 137 * (Clearly, a task raising the refcount on its own ipc_ns 138 * needn't take mq_lock since it can't race with the last task 139 * in the ipcns exiting). 140 */ 141 void put_ipc_ns(struct ipc_namespace *ns) 142 { 143 if (atomic_dec_and_lock(&ns->count, &mq_lock)) { 144 mq_clear_sbinfo(ns); 145 spin_unlock(&mq_lock); 146 mq_put_mnt(ns); 147 free_ipc_ns(ns); 148 } 149 } 150 151 static void *ipcns_get(struct task_struct *task) 152 { 153 struct ipc_namespace *ns = NULL; 154 struct nsproxy *nsproxy; 155 156 rcu_read_lock(); 157 nsproxy = task_nsproxy(task); 158 if (nsproxy) 159 ns = get_ipc_ns(nsproxy->ipc_ns); 160 rcu_read_unlock(); 161 162 return ns; 163 } 164 165 static void ipcns_put(void *ns) 166 { 167 return put_ipc_ns(ns); 168 } 169 170 static int ipcns_install(struct nsproxy *nsproxy, void *new) 171 { 172 struct ipc_namespace *ns = new; 173 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 174 !nsown_capable(CAP_SYS_ADMIN)) 175 return -EPERM; 176 177 /* Ditch state from the old ipc namespace */ 178 exit_sem(current); 179 put_ipc_ns(nsproxy->ipc_ns); 180 nsproxy->ipc_ns = get_ipc_ns(ns); 181 return 0; 182 } 183 184 static unsigned int ipcns_inum(void *vp) 185 { 186 struct ipc_namespace *ns = vp; 187 188 return ns->proc_inum; 189 } 190 191 const struct proc_ns_operations ipcns_operations = { 192 .name = "ipc", 193 .type = CLONE_NEWIPC, 194 .get = ipcns_get, 195 .put = ipcns_put, 196 .install = ipcns_install, 197 .inum = ipcns_inum, 198 }; 199