1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/ipc/namespace.c 4 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc. 5 */ 6 7 #include <linux/ipc.h> 8 #include <linux/msg.h> 9 #include <linux/ipc_namespace.h> 10 #include <linux/rcupdate.h> 11 #include <linux/nsproxy.h> 12 #include <linux/slab.h> 13 #include <linux/cred.h> 14 #include <linux/fs.h> 15 #include <linux/mount.h> 16 #include <linux/user_namespace.h> 17 #include <linux/proc_ns.h> 18 #include <linux/nstree.h> 19 #include <linux/sched/task.h> 20 21 #include "util.h" 22 23 /* 24 * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount. 25 */ 26 static void free_ipc(struct work_struct *unused); 27 static DECLARE_WORK(free_ipc_work, free_ipc); 28 29 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns) 30 { 31 return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES); 32 } 33 34 static void dec_ipc_namespaces(struct ucounts *ucounts) 35 { 36 dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES); 37 } 38 39 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns, 40 struct ipc_namespace *old_ns) 41 { 42 struct ipc_namespace *ns; 43 struct ucounts *ucounts; 44 int err; 45 46 err = -ENOSPC; 47 again: 48 ucounts = inc_ipc_namespaces(user_ns); 49 if (!ucounts) { 50 /* 51 * IPC namespaces are freed asynchronously, by free_ipc_work. 52 * If frees were pending, flush_work will wait, and 53 * return true. Fail the allocation if no frees are pending. 54 */ 55 if (flush_work(&free_ipc_work)) 56 goto again; 57 goto fail; 58 } 59 60 err = -ENOMEM; 61 ns = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL_ACCOUNT); 62 if (ns == NULL) 63 goto fail_dec; 64 65 err = ns_common_init(ns); 66 if (err) 67 goto fail_free; 68 69 ns_tree_gen_id(ns); 70 ns->user_ns = get_user_ns(user_ns); 71 ns->ucounts = ucounts; 72 73 err = mq_init_ns(ns); 74 if (err) 75 goto fail_put; 76 77 err = -ENOMEM; 78 if (!setup_mq_sysctls(ns)) 79 goto fail_mq_mount; 80 81 if (!setup_ipc_sysctls(ns)) 82 goto fail_mq_sysctls; 83 84 err = msg_init_ns(ns); 85 if (err) 86 goto fail_ipc; 87 88 sem_init_ns(ns); 89 shm_init_ns(ns); 90 ns_tree_add_raw(ns); 91 92 return ns; 93 94 fail_ipc: 95 retire_ipc_sysctls(ns); 96 fail_mq_sysctls: 97 retire_mq_sysctls(ns); 98 fail_mq_mount: 99 mntput(ns->mq_mnt); 100 fail_put: 101 put_user_ns(ns->user_ns); 102 ns_common_free(ns); 103 fail_free: 104 kfree(ns); 105 fail_dec: 106 dec_ipc_namespaces(ucounts); 107 fail: 108 return ERR_PTR(err); 109 } 110 111 struct ipc_namespace *copy_ipcs(u64 flags, 112 struct user_namespace *user_ns, struct ipc_namespace *ns) 113 { 114 if (!(flags & CLONE_NEWIPC)) 115 return get_ipc_ns(ns); 116 return create_ipc_ns(user_ns, ns); 117 } 118 119 /* 120 * free_ipcs - free all ipcs of one type 121 * @ns: the namespace to remove the ipcs from 122 * @ids: the table of ipcs to free 123 * @free: the function called to free each individual ipc 124 * 125 * Called for each kind of ipc when an ipc_namespace exits. 126 */ 127 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, 128 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) 129 { 130 struct kern_ipc_perm *perm; 131 int next_id; 132 int total, in_use; 133 134 down_write(&ids->rwsem); 135 136 in_use = ids->in_use; 137 138 for (total = 0, next_id = 0; total < in_use; next_id++) { 139 perm = idr_find(&ids->ipcs_idr, next_id); 140 if (perm == NULL) 141 continue; 142 rcu_read_lock(); 143 ipc_lock_object(perm); 144 free(ns, perm); 145 total++; 146 } 147 up_write(&ids->rwsem); 148 } 149 150 static void free_ipc_ns(struct ipc_namespace *ns) 151 { 152 /* 153 * Caller needs to wait for an RCU grace period to have passed 154 * after making the mount point inaccessible to new accesses. 155 */ 156 mntput(ns->mq_mnt); 157 sem_exit_ns(ns); 158 msg_exit_ns(ns); 159 shm_exit_ns(ns); 160 161 retire_mq_sysctls(ns); 162 retire_ipc_sysctls(ns); 163 164 dec_ipc_namespaces(ns->ucounts); 165 put_user_ns(ns->user_ns); 166 ns_common_free(ns); 167 kfree(ns); 168 } 169 170 static LLIST_HEAD(free_ipc_list); 171 static void free_ipc(struct work_struct *unused) 172 { 173 struct llist_node *node = llist_del_all(&free_ipc_list); 174 struct ipc_namespace *n, *t; 175 176 llist_for_each_entry_safe(n, t, node, mnt_llist) 177 mnt_make_shortterm(n->mq_mnt); 178 179 /* Wait for any last users to have gone away. */ 180 synchronize_rcu(); 181 182 llist_for_each_entry_safe(n, t, node, mnt_llist) 183 free_ipc_ns(n); 184 } 185 186 /* 187 * put_ipc_ns - drop a reference to an ipc namespace. 188 * @ns: the namespace to put 189 * 190 * If this is the last task in the namespace exiting, and 191 * it is dropping the refcount to 0, then it can race with 192 * a task in another ipc namespace but in a mounts namespace 193 * which has this ipcns's mqueuefs mounted, doing some action 194 * with one of the mqueuefs files. That can raise the refcount. 195 * So dropping the refcount, and raising the refcount when 196 * accessing it through the VFS, are protected with mq_lock. 197 * 198 * (Clearly, a task raising the refcount on its own ipc_ns 199 * needn't take mq_lock since it can't race with the last task 200 * in the ipcns exiting). 201 */ 202 void put_ipc_ns(struct ipc_namespace *ns) 203 { 204 if (ns_ref_put_and_lock(ns, &mq_lock)) { 205 mq_clear_sbinfo(ns); 206 spin_unlock(&mq_lock); 207 208 ns_tree_remove(ns); 209 if (llist_add(&ns->mnt_llist, &free_ipc_list)) 210 schedule_work(&free_ipc_work); 211 } 212 } 213 214 static struct ns_common *ipcns_get(struct task_struct *task) 215 { 216 struct ipc_namespace *ns = NULL; 217 struct nsproxy *nsproxy; 218 219 task_lock(task); 220 nsproxy = task->nsproxy; 221 if (nsproxy) 222 ns = get_ipc_ns(nsproxy->ipc_ns); 223 task_unlock(task); 224 225 return ns ? &ns->ns : NULL; 226 } 227 228 static void ipcns_put(struct ns_common *ns) 229 { 230 return put_ipc_ns(to_ipc_ns(ns)); 231 } 232 233 static int ipcns_install(struct nsset *nsset, struct ns_common *new) 234 { 235 struct nsproxy *nsproxy = nsset->nsproxy; 236 struct ipc_namespace *ns = to_ipc_ns(new); 237 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 238 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) 239 return -EPERM; 240 241 put_ipc_ns(nsproxy->ipc_ns); 242 nsproxy->ipc_ns = get_ipc_ns(ns); 243 return 0; 244 } 245 246 static struct user_namespace *ipcns_owner(struct ns_common *ns) 247 { 248 return to_ipc_ns(ns)->user_ns; 249 } 250 251 const struct proc_ns_operations ipcns_operations = { 252 .name = "ipc", 253 .get = ipcns_get, 254 .put = ipcns_put, 255 .install = ipcns_install, 256 .owner = ipcns_owner, 257 }; 258