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 47 sem_init_ns(ns); 48 msg_init_ns(ns); 49 shm_init_ns(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 99 put_user_ns(ns->user_ns); 100 ns_free_inum(&ns->ns); 101 kfree(ns); 102 } 103 104 /* 105 * put_ipc_ns - drop a reference to an ipc namespace. 106 * @ns: the namespace to put 107 * 108 * If this is the last task in the namespace exiting, and 109 * it is dropping the refcount to 0, then it can race with 110 * a task in another ipc namespace but in a mounts namespace 111 * which has this ipcns's mqueuefs mounted, doing some action 112 * with one of the mqueuefs files. That can raise the refcount. 113 * So dropping the refcount, and raising the refcount when 114 * accessing it through the VFS, are protected with mq_lock. 115 * 116 * (Clearly, a task raising the refcount on its own ipc_ns 117 * needn't take mq_lock since it can't race with the last task 118 * in the ipcns exiting). 119 */ 120 void put_ipc_ns(struct ipc_namespace *ns) 121 { 122 if (atomic_dec_and_lock(&ns->count, &mq_lock)) { 123 mq_clear_sbinfo(ns); 124 spin_unlock(&mq_lock); 125 mq_put_mnt(ns); 126 free_ipc_ns(ns); 127 } 128 } 129 130 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns) 131 { 132 return container_of(ns, struct ipc_namespace, ns); 133 } 134 135 static struct ns_common *ipcns_get(struct task_struct *task) 136 { 137 struct ipc_namespace *ns = NULL; 138 struct nsproxy *nsproxy; 139 140 task_lock(task); 141 nsproxy = task->nsproxy; 142 if (nsproxy) 143 ns = get_ipc_ns(nsproxy->ipc_ns); 144 task_unlock(task); 145 146 return ns ? &ns->ns : NULL; 147 } 148 149 static void ipcns_put(struct ns_common *ns) 150 { 151 return put_ipc_ns(to_ipc_ns(ns)); 152 } 153 154 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new) 155 { 156 struct ipc_namespace *ns = to_ipc_ns(new); 157 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 158 !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) 159 return -EPERM; 160 161 /* Ditch state from the old ipc namespace */ 162 exit_sem(current); 163 put_ipc_ns(nsproxy->ipc_ns); 164 nsproxy->ipc_ns = get_ipc_ns(ns); 165 return 0; 166 } 167 168 const struct proc_ns_operations ipcns_operations = { 169 .name = "ipc", 170 .type = CLONE_NEWIPC, 171 .get = ipcns_get, 172 .put = ipcns_put, 173 .install = ipcns_install, 174 }; 175