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_ns.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 = ns_alloc_inum(&ns->ns); 30 if (err) { 31 kfree(ns); 32 return ERR_PTR(err); 33 } 34 ns->ns.ops = &ipcns_operations; 35 36 atomic_set(&ns->count, 1); 37 ns->user_ns = get_user_ns(user_ns); 38 39 err = mq_init_ns(ns); 40 if (err) { 41 put_user_ns(ns->user_ns); 42 ns_free_inum(&ns->ns); 43 kfree(ns); 44 return ERR_PTR(err); 45 } 46 atomic_inc(&nr_ipc_ns); 47 48 sem_init_ns(ns); 49 msg_init_ns(ns); 50 shm_init_ns(ns); 51 52 return ns; 53 } 54 55 struct ipc_namespace *copy_ipcs(unsigned long flags, 56 struct user_namespace *user_ns, struct ipc_namespace *ns) 57 { 58 if (!(flags & CLONE_NEWIPC)) 59 return get_ipc_ns(ns); 60 return create_ipc_ns(user_ns, ns); 61 } 62 63 /* 64 * free_ipcs - free all ipcs of one type 65 * @ns: the namespace to remove the ipcs from 66 * @ids: the table of ipcs to free 67 * @free: the function called to free each individual ipc 68 * 69 * Called for each kind of ipc when an ipc_namespace exits. 70 */ 71 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, 72 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) 73 { 74 struct kern_ipc_perm *perm; 75 int next_id; 76 int total, in_use; 77 78 down_write(&ids->rwsem); 79 80 in_use = ids->in_use; 81 82 for (total = 0, next_id = 0; total < in_use; next_id++) { 83 perm = idr_find(&ids->ipcs_idr, next_id); 84 if (perm == NULL) 85 continue; 86 rcu_read_lock(); 87 ipc_lock_object(perm); 88 free(ns, perm); 89 total++; 90 } 91 up_write(&ids->rwsem); 92 } 93 94 static void free_ipc_ns(struct ipc_namespace *ns) 95 { 96 sem_exit_ns(ns); 97 msg_exit_ns(ns); 98 shm_exit_ns(ns); 99 atomic_dec(&nr_ipc_ns); 100 101 put_user_ns(ns->user_ns); 102 ns_free_inum(&ns->ns); 103 kfree(ns); 104 } 105 106 /* 107 * put_ipc_ns - drop a reference to an ipc namespace. 108 * @ns: the namespace to put 109 * 110 * If this is the last task in the namespace exiting, and 111 * it is dropping the refcount to 0, then it can race with 112 * a task in another ipc namespace but in a mounts namespace 113 * which has this ipcns's mqueuefs mounted, doing some action 114 * with one of the mqueuefs files. That can raise the refcount. 115 * So dropping the refcount, and raising the refcount when 116 * accessing it through the VFS, are protected with mq_lock. 117 * 118 * (Clearly, a task raising the refcount on its own ipc_ns 119 * needn't take mq_lock since it can't race with the last task 120 * in the ipcns exiting). 121 */ 122 void put_ipc_ns(struct ipc_namespace *ns) 123 { 124 if (atomic_dec_and_lock(&ns->count, &mq_lock)) { 125 mq_clear_sbinfo(ns); 126 spin_unlock(&mq_lock); 127 mq_put_mnt(ns); 128 free_ipc_ns(ns); 129 } 130 } 131 132 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns) 133 { 134 return container_of(ns, struct ipc_namespace, ns); 135 } 136 137 static struct ns_common *ipcns_get(struct task_struct *task) 138 { 139 struct ipc_namespace *ns = NULL; 140 struct nsproxy *nsproxy; 141 142 task_lock(task); 143 nsproxy = task->nsproxy; 144 if (nsproxy) 145 ns = get_ipc_ns(nsproxy->ipc_ns); 146 task_unlock(task); 147 148 return ns ? &ns->ns : NULL; 149 } 150 151 static void ipcns_put(struct ns_common *ns) 152 { 153 return put_ipc_ns(to_ipc_ns(ns)); 154 } 155 156 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new) 157 { 158 struct ipc_namespace *ns = to_ipc_ns(new); 159 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 160 !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) 161 return -EPERM; 162 163 /* Ditch state from the old ipc namespace */ 164 exit_sem(current); 165 put_ipc_ns(nsproxy->ipc_ns); 166 nsproxy->ipc_ns = get_ipc_ns(ns); 167 return 0; 168 } 169 170 const struct proc_ns_operations ipcns_operations = { 171 .name = "ipc", 172 .type = CLONE_NEWIPC, 173 .get = ipcns_get, 174 .put = ipcns_put, 175 .install = ipcns_install, 176 }; 177