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