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/sched/task.h> 19 20 #include "util.h" 21 22 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns) 23 { 24 return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES); 25 } 26 27 static void dec_ipc_namespaces(struct ucounts *ucounts) 28 { 29 dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES); 30 } 31 32 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns, 33 struct ipc_namespace *old_ns) 34 { 35 struct ipc_namespace *ns; 36 struct ucounts *ucounts; 37 int err; 38 39 err = -ENOSPC; 40 ucounts = inc_ipc_namespaces(user_ns); 41 if (!ucounts) 42 goto fail; 43 44 err = -ENOMEM; 45 ns = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL); 46 if (ns == NULL) 47 goto fail_dec; 48 49 err = ns_alloc_inum(&ns->ns); 50 if (err) 51 goto fail_free; 52 ns->ns.ops = &ipcns_operations; 53 54 refcount_set(&ns->ns.count, 1); 55 ns->user_ns = get_user_ns(user_ns); 56 ns->ucounts = ucounts; 57 58 err = mq_init_ns(ns); 59 if (err) 60 goto fail_put; 61 62 sem_init_ns(ns); 63 msg_init_ns(ns); 64 shm_init_ns(ns); 65 66 return ns; 67 68 fail_put: 69 put_user_ns(ns->user_ns); 70 ns_free_inum(&ns->ns); 71 fail_free: 72 kfree(ns); 73 fail_dec: 74 dec_ipc_namespaces(ucounts); 75 fail: 76 return ERR_PTR(err); 77 } 78 79 struct ipc_namespace *copy_ipcs(unsigned long flags, 80 struct user_namespace *user_ns, struct ipc_namespace *ns) 81 { 82 if (!(flags & CLONE_NEWIPC)) 83 return get_ipc_ns(ns); 84 return create_ipc_ns(user_ns, ns); 85 } 86 87 /* 88 * free_ipcs - free all ipcs of one type 89 * @ns: the namespace to remove the ipcs from 90 * @ids: the table of ipcs to free 91 * @free: the function called to free each individual ipc 92 * 93 * Called for each kind of ipc when an ipc_namespace exits. 94 */ 95 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, 96 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) 97 { 98 struct kern_ipc_perm *perm; 99 int next_id; 100 int total, in_use; 101 102 down_write(&ids->rwsem); 103 104 in_use = ids->in_use; 105 106 for (total = 0, next_id = 0; total < in_use; next_id++) { 107 perm = idr_find(&ids->ipcs_idr, next_id); 108 if (perm == NULL) 109 continue; 110 rcu_read_lock(); 111 ipc_lock_object(perm); 112 free(ns, perm); 113 total++; 114 } 115 up_write(&ids->rwsem); 116 } 117 118 static void free_ipc_ns(struct ipc_namespace *ns) 119 { 120 /* mq_put_mnt() waits for a grace period as kern_unmount() 121 * uses synchronize_rcu(). 122 */ 123 mq_put_mnt(ns); 124 sem_exit_ns(ns); 125 msg_exit_ns(ns); 126 shm_exit_ns(ns); 127 128 dec_ipc_namespaces(ns->ucounts); 129 put_user_ns(ns->user_ns); 130 ns_free_inum(&ns->ns); 131 kfree(ns); 132 } 133 134 static LLIST_HEAD(free_ipc_list); 135 static void free_ipc(struct work_struct *unused) 136 { 137 struct llist_node *node = llist_del_all(&free_ipc_list); 138 struct ipc_namespace *n, *t; 139 140 llist_for_each_entry_safe(n, t, node, mnt_llist) 141 free_ipc_ns(n); 142 } 143 144 /* 145 * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount. 146 */ 147 static DECLARE_WORK(free_ipc_work, free_ipc); 148 149 /* 150 * put_ipc_ns - drop a reference to an ipc namespace. 151 * @ns: the namespace to put 152 * 153 * If this is the last task in the namespace exiting, and 154 * it is dropping the refcount to 0, then it can race with 155 * a task in another ipc namespace but in a mounts namespace 156 * which has this ipcns's mqueuefs mounted, doing some action 157 * with one of the mqueuefs files. That can raise the refcount. 158 * So dropping the refcount, and raising the refcount when 159 * accessing it through the VFS, are protected with mq_lock. 160 * 161 * (Clearly, a task raising the refcount on its own ipc_ns 162 * needn't take mq_lock since it can't race with the last task 163 * in the ipcns exiting). 164 */ 165 void put_ipc_ns(struct ipc_namespace *ns) 166 { 167 if (refcount_dec_and_lock(&ns->ns.count, &mq_lock)) { 168 mq_clear_sbinfo(ns); 169 spin_unlock(&mq_lock); 170 171 if (llist_add(&ns->mnt_llist, &free_ipc_list)) 172 schedule_work(&free_ipc_work); 173 } 174 } 175 176 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns) 177 { 178 return container_of(ns, struct ipc_namespace, ns); 179 } 180 181 static struct ns_common *ipcns_get(struct task_struct *task) 182 { 183 struct ipc_namespace *ns = NULL; 184 struct nsproxy *nsproxy; 185 186 task_lock(task); 187 nsproxy = task->nsproxy; 188 if (nsproxy) 189 ns = get_ipc_ns(nsproxy->ipc_ns); 190 task_unlock(task); 191 192 return ns ? &ns->ns : NULL; 193 } 194 195 static void ipcns_put(struct ns_common *ns) 196 { 197 return put_ipc_ns(to_ipc_ns(ns)); 198 } 199 200 static int ipcns_install(struct nsset *nsset, struct ns_common *new) 201 { 202 struct nsproxy *nsproxy = nsset->nsproxy; 203 struct ipc_namespace *ns = to_ipc_ns(new); 204 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 205 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) 206 return -EPERM; 207 208 put_ipc_ns(nsproxy->ipc_ns); 209 nsproxy->ipc_ns = get_ipc_ns(ns); 210 return 0; 211 } 212 213 static struct user_namespace *ipcns_owner(struct ns_common *ns) 214 { 215 return to_ipc_ns(ns)->user_ns; 216 } 217 218 const struct proc_ns_operations ipcns_operations = { 219 .name = "ipc", 220 .type = CLONE_NEWIPC, 221 .get = ipcns_get, 222 .put = ipcns_put, 223 .install = ipcns_install, 224 .owner = ipcns_owner, 225 }; 226