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 = kmalloc(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->count, 1); 55 ns->user_ns = get_user_ns(user_ns); 56 ns->ucounts = ucounts; 57 58 err = sem_init_ns(ns); 59 if (err) 60 goto fail_put; 61 err = msg_init_ns(ns); 62 if (err) 63 goto fail_destroy_sem; 64 err = shm_init_ns(ns); 65 if (err) 66 goto fail_destroy_msg; 67 68 err = mq_init_ns(ns); 69 if (err) 70 goto fail_destroy_shm; 71 72 return ns; 73 74 fail_destroy_shm: 75 shm_exit_ns(ns); 76 fail_destroy_msg: 77 msg_exit_ns(ns); 78 fail_destroy_sem: 79 sem_exit_ns(ns); 80 fail_put: 81 put_user_ns(ns->user_ns); 82 ns_free_inum(&ns->ns); 83 fail_free: 84 kfree(ns); 85 fail_dec: 86 dec_ipc_namespaces(ucounts); 87 fail: 88 return ERR_PTR(err); 89 } 90 91 struct ipc_namespace *copy_ipcs(unsigned long flags, 92 struct user_namespace *user_ns, struct ipc_namespace *ns) 93 { 94 if (!(flags & CLONE_NEWIPC)) 95 return get_ipc_ns(ns); 96 return create_ipc_ns(user_ns, ns); 97 } 98 99 /* 100 * free_ipcs - free all ipcs of one type 101 * @ns: the namespace to remove the ipcs from 102 * @ids: the table of ipcs to free 103 * @free: the function called to free each individual ipc 104 * 105 * Called for each kind of ipc when an ipc_namespace exits. 106 */ 107 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, 108 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) 109 { 110 struct kern_ipc_perm *perm; 111 int next_id; 112 int total, in_use; 113 114 down_write(&ids->rwsem); 115 116 in_use = ids->in_use; 117 118 for (total = 0, next_id = 0; total < in_use; next_id++) { 119 perm = idr_find(&ids->ipcs_idr, next_id); 120 if (perm == NULL) 121 continue; 122 rcu_read_lock(); 123 ipc_lock_object(perm); 124 free(ns, perm); 125 total++; 126 } 127 up_write(&ids->rwsem); 128 } 129 130 static void free_ipc_ns(struct ipc_namespace *ns) 131 { 132 sem_exit_ns(ns); 133 msg_exit_ns(ns); 134 shm_exit_ns(ns); 135 136 dec_ipc_namespaces(ns->ucounts); 137 put_user_ns(ns->user_ns); 138 ns_free_inum(&ns->ns); 139 kfree(ns); 140 } 141 142 /* 143 * put_ipc_ns - drop a reference to an ipc namespace. 144 * @ns: the namespace to put 145 * 146 * If this is the last task in the namespace exiting, and 147 * it is dropping the refcount to 0, then it can race with 148 * a task in another ipc namespace but in a mounts namespace 149 * which has this ipcns's mqueuefs mounted, doing some action 150 * with one of the mqueuefs files. That can raise the refcount. 151 * So dropping the refcount, and raising the refcount when 152 * accessing it through the VFS, are protected with mq_lock. 153 * 154 * (Clearly, a task raising the refcount on its own ipc_ns 155 * needn't take mq_lock since it can't race with the last task 156 * in the ipcns exiting). 157 */ 158 void put_ipc_ns(struct ipc_namespace *ns) 159 { 160 if (refcount_dec_and_lock(&ns->count, &mq_lock)) { 161 mq_clear_sbinfo(ns); 162 spin_unlock(&mq_lock); 163 mq_put_mnt(ns); 164 free_ipc_ns(ns); 165 } 166 } 167 168 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns) 169 { 170 return container_of(ns, struct ipc_namespace, ns); 171 } 172 173 static struct ns_common *ipcns_get(struct task_struct *task) 174 { 175 struct ipc_namespace *ns = NULL; 176 struct nsproxy *nsproxy; 177 178 task_lock(task); 179 nsproxy = task->nsproxy; 180 if (nsproxy) 181 ns = get_ipc_ns(nsproxy->ipc_ns); 182 task_unlock(task); 183 184 return ns ? &ns->ns : NULL; 185 } 186 187 static void ipcns_put(struct ns_common *ns) 188 { 189 return put_ipc_ns(to_ipc_ns(ns)); 190 } 191 192 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new) 193 { 194 struct ipc_namespace *ns = to_ipc_ns(new); 195 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || 196 !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) 197 return -EPERM; 198 199 /* Ditch state from the old ipc namespace */ 200 exit_sem(current); 201 put_ipc_ns(nsproxy->ipc_ns); 202 nsproxy->ipc_ns = get_ipc_ns(ns); 203 return 0; 204 } 205 206 static struct user_namespace *ipcns_owner(struct ns_common *ns) 207 { 208 return to_ipc_ns(ns)->user_ns; 209 } 210 211 const struct proc_ns_operations ipcns_operations = { 212 .name = "ipc", 213 .type = CLONE_NEWIPC, 214 .get = ipcns_get, 215 .put = ipcns_put, 216 .install = ipcns_install, 217 .owner = ipcns_owner, 218 }; 219