kernel/nsproxy.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  Copyright (C) 2006 IBM Corporation
   4  *
   5  *  Author: Serge Hallyn <serue@us.ibm.com>
   6  *
   7  *  Jun 2006 - namespaces support
   8  *             OpenVZ, SWsoft Inc.
   9  *             Pavel Emelianov <xemul@openvz.org>
  10  */
  11
  12 #include <linux/slab.h>
  13 #include <linux/export.h>
  14 #include <linux/nsproxy.h>
  15 #include <linux/init_task.h>
  16 #include <linux/mnt_namespace.h>
  17 #include <linux/utsname.h>
  18 #include <linux/pid_namespace.h>
  19 #include <net/net_namespace.h>
  20 #include <linux/ipc_namespace.h>
  21 #include <linux/time_namespace.h>
  22 #include <linux/fs_struct.h>
  23 #include <linux/proc_fs.h>
  24 #include <linux/proc_ns.h>
  25 #include <linux/file.h>
  26 #include <linux/syscalls.h>
  27 #include <linux/cgroup.h>
  28 #include <linux/perf_event.h>
  29
  30 static struct kmem_cache *nsproxy_cachep;
  31
  32 struct nsproxy init_nsproxy = {
  33         .count                  = ATOMIC_INIT(1),
  34         .uts_ns                 = &init_uts_ns,
  35 #if defined(CONFIG_POSIX_MQUEUE) || defined(CONFIG_SYSVIPC)
  36         .ipc_ns                 = &init_ipc_ns,
  37 #endif
  38         .mnt_ns                 = NULL,
  39         .pid_ns_for_children    = &init_pid_ns,
  40 #ifdef CONFIG_NET
  41         .net_ns                 = &init_net,
  42 #endif
  43 #ifdef CONFIG_CGROUPS
  44         .cgroup_ns              = &init_cgroup_ns,
  45 #endif
  46 #ifdef CONFIG_TIME_NS
  47         .time_ns                = &init_time_ns,
  48         .time_ns_for_children   = &init_time_ns,
  49 #endif
  50 };
  51
  52 static inline struct nsproxy *create_nsproxy(void)
  53 {
  54         struct nsproxy *nsproxy;
  55
  56         nsproxy = kmem_cache_alloc(nsproxy_cachep, GFP_KERNEL);
  57         if (nsproxy)
  58                 atomic_set(&nsproxy->count, 1);
  59         return nsproxy;
  60 }
  61
  62 /*
  63  * Create new nsproxy and all of its the associated namespaces.
  64  * Return the newly created nsproxy.  Do not attach this to the task,
  65  * leave it to the caller to do proper locking and attach it to task.
  66  */
  67 static struct nsproxy *create_new_namespaces(unsigned long flags,
  68         struct task_struct *tsk, struct user_namespace *user_ns,
  69         struct fs_struct *new_fs)
  70 {
  71         struct nsproxy *new_nsp;
  72         int err;
  73
  74         new_nsp = create_nsproxy();
  75         if (!new_nsp)
  76                 return ERR_PTR(-ENOMEM);
  77
  78         new_nsp->mnt_ns = copy_mnt_ns(flags, tsk->nsproxy->mnt_ns, user_ns, new_fs);
  79         if (IS_ERR(new_nsp->mnt_ns)) {
  80                 err = PTR_ERR(new_nsp->mnt_ns);
  81                 goto out_ns;
  82         }
  83
  84         new_nsp->uts_ns = copy_utsname(flags, user_ns, tsk->nsproxy->uts_ns);
  85         if (IS_ERR(new_nsp->uts_ns)) {
  86                 err = PTR_ERR(new_nsp->uts_ns);
  87                 goto out_uts;
  88         }
  89
  90         new_nsp->ipc_ns = copy_ipcs(flags, user_ns, tsk->nsproxy->ipc_ns);
  91         if (IS_ERR(new_nsp->ipc_ns)) {
  92                 err = PTR_ERR(new_nsp->ipc_ns);
  93                 goto out_ipc;
  94         }
  95
  96         new_nsp->pid_ns_for_children =
  97                 copy_pid_ns(flags, user_ns, tsk->nsproxy->pid_ns_for_children);
  98         if (IS_ERR(new_nsp->pid_ns_for_children)) {
  99                 err = PTR_ERR(new_nsp->pid_ns_for_children);
 100                 goto out_pid;
 101         }
 102
 103         new_nsp->cgroup_ns = copy_cgroup_ns(flags, user_ns,
 104                                             tsk->nsproxy->cgroup_ns);
 105         if (IS_ERR(new_nsp->cgroup_ns)) {
 106                 err = PTR_ERR(new_nsp->cgroup_ns);
 107                 goto out_cgroup;
 108         }
 109
 110         new_nsp->net_ns = copy_net_ns(flags, user_ns, tsk->nsproxy->net_ns);
 111         if (IS_ERR(new_nsp->net_ns)) {
 112                 err = PTR_ERR(new_nsp->net_ns);
 113                 goto out_net;
 114         }
 115
 116         new_nsp->time_ns_for_children = copy_time_ns(flags, user_ns,
 117                                         tsk->nsproxy->time_ns_for_children);
 118         if (IS_ERR(new_nsp->time_ns_for_children)) {
 119                 err = PTR_ERR(new_nsp->time_ns_for_children);
 120                 goto out_time;
 121         }
 122         new_nsp->time_ns = get_time_ns(tsk->nsproxy->time_ns);
 123
 124         return new_nsp;
 125
 126 out_time:
 127         put_net(new_nsp->net_ns);
 128 out_net:
 129         put_cgroup_ns(new_nsp->cgroup_ns);
 130 out_cgroup:
 131         if (new_nsp->pid_ns_for_children)
 132                 put_pid_ns(new_nsp->pid_ns_for_children);
 133 out_pid:
 134         if (new_nsp->ipc_ns)
 135                 put_ipc_ns(new_nsp->ipc_ns);
 136 out_ipc:
 137         if (new_nsp->uts_ns)
 138                 put_uts_ns(new_nsp->uts_ns);
 139 out_uts:
 140         if (new_nsp->mnt_ns)
 141                 put_mnt_ns(new_nsp->mnt_ns);
 142 out_ns:
 143         kmem_cache_free(nsproxy_cachep, new_nsp);
 144         return ERR_PTR(err);
 145 }
 146
 147 /*
 148  * called from clone.  This now handles copy for nsproxy and all
 149  * namespaces therein.
 150  */
 151 int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 152 {
 153         struct nsproxy *old_ns = tsk->nsproxy;
 154         struct user_namespace *user_ns = task_cred_xxx(tsk, user_ns);
 155         struct nsproxy *new_ns;
 156         int ret;
 157
 158         if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
 159                               CLONE_NEWPID | CLONE_NEWNET |
 160                               CLONE_NEWCGROUP | CLONE_NEWTIME)))) {
 161                 if (likely(old_ns->time_ns_for_children == old_ns->time_ns)) {
 162                         get_nsproxy(old_ns);
 163                         return 0;
 164                 }
 165         } else if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 166                 return -EPERM;
 167
 168         /*
 169          * CLONE_NEWIPC must detach from the undolist: after switching
 170          * to a new ipc namespace, the semaphore arrays from the old
 171          * namespace are unreachable.  In clone parlance, CLONE_SYSVSEM
 172          * means share undolist with parent, so we must forbid using
 173          * it along with CLONE_NEWIPC.
 174          */
 175         if ((flags & (CLONE_NEWIPC | CLONE_SYSVSEM)) ==
 176                 (CLONE_NEWIPC | CLONE_SYSVSEM))
 177                 return -EINVAL;
 178
 179         new_ns = create_new_namespaces(flags, tsk, user_ns, tsk->fs);
 180         if (IS_ERR(new_ns))
 181                 return  PTR_ERR(new_ns);
 182
 183         ret = timens_on_fork(new_ns, tsk);
 184         if (ret) {
 185                 free_nsproxy(new_ns);
 186                 return ret;
 187         }
 188
 189         tsk->nsproxy = new_ns;
 190         return 0;
 191 }
 192
 193 void free_nsproxy(struct nsproxy *ns)
 194 {
 195         if (ns->mnt_ns)
 196                 put_mnt_ns(ns->mnt_ns);
 197         if (ns->uts_ns)
 198                 put_uts_ns(ns->uts_ns);
 199         if (ns->ipc_ns)
 200                 put_ipc_ns(ns->ipc_ns);
 201         if (ns->pid_ns_for_children)
 202                 put_pid_ns(ns->pid_ns_for_children);
 203         if (ns->time_ns)
 204                 put_time_ns(ns->time_ns);
 205         if (ns->time_ns_for_children)
 206                 put_time_ns(ns->time_ns_for_children);
 207         put_cgroup_ns(ns->cgroup_ns);
 208         put_net(ns->net_ns);
 209         kmem_cache_free(nsproxy_cachep, ns);
 210 }
 211
 212 /*
 213  * Called from unshare. Unshare all the namespaces part of nsproxy.
 214  * On success, returns the new nsproxy.
 215  */
 216 int unshare_nsproxy_namespaces(unsigned long unshare_flags,
 217         struct nsproxy **new_nsp, struct cred *new_cred, struct fs_struct *new_fs)
 218 {
 219         struct user_namespace *user_ns;
 220         int err = 0;
 221
 222         if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
 223                                CLONE_NEWNET | CLONE_NEWPID | CLONE_NEWCGROUP |
 224                                CLONE_NEWTIME)))
 225                 return 0;
 226
 227         user_ns = new_cred ? new_cred->user_ns : current_user_ns();
 228         if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 229                 return -EPERM;
 230
 231         *new_nsp = create_new_namespaces(unshare_flags, current, user_ns,
 232                                          new_fs ? new_fs : current->fs);
 233         if (IS_ERR(*new_nsp)) {
 234                 err = PTR_ERR(*new_nsp);
 235                 goto out;
 236         }
 237
 238 out:
 239         return err;
 240 }
 241
 242 void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
 243 {
 244         struct nsproxy *ns;
 245
 246         might_sleep();
 247
 248         task_lock(p);
 249         ns = p->nsproxy;
 250         p->nsproxy = new;
 251         task_unlock(p);
 252
 253         if (ns && atomic_dec_and_test(&ns->count))
 254                 free_nsproxy(ns);
 255 }
 256
 257 void exit_task_namespaces(struct task_struct *p)
 258 {
 259         switch_task_namespaces(p, NULL);
 260 }
 261
 262 static int check_setns_flags(unsigned long flags)
 263 {
 264         if (!flags || (flags & ~(CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
 265                                  CLONE_NEWNET | CLONE_NEWUSER | CLONE_NEWPID |
 266                                  CLONE_NEWCGROUP)))
 267                 return -EINVAL;
 268
 269 #ifndef CONFIG_USER_NS
 270         if (flags & CLONE_NEWUSER)
 271                 return -EINVAL;
 272 #endif
 273 #ifndef CONFIG_PID_NS
 274         if (flags & CLONE_NEWPID)
 275                 return -EINVAL;
 276 #endif
 277 #ifndef CONFIG_UTS_NS
 278         if (flags & CLONE_NEWUTS)
 279                 return -EINVAL;
 280 #endif
 281 #ifndef CONFIG_IPC_NS
 282         if (flags & CLONE_NEWIPC)
 283                 return -EINVAL;
 284 #endif
 285 #ifndef CONFIG_CGROUPS
 286         if (flags & CLONE_NEWCGROUP)
 287                 return -EINVAL;
 288 #endif
 289 #ifndef CONFIG_NET_NS
 290         if (flags & CLONE_NEWNET)
 291                 return -EINVAL;
 292 #endif
 293
 294         return 0;
 295 }
 296
 297 static void put_nsset(struct nsset *nsset)
 298 {
 299         unsigned flags = nsset->flags;
 300
 301         if (flags & CLONE_NEWUSER)
 302                 put_cred(nsset_cred(nsset));
 303         /*
 304          * We only created a temporary copy if we attached to more than just
 305          * the mount namespace.
 306          */
 307         if (nsset->fs && (flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS))
 308                 free_fs_struct(nsset->fs);
 309         if (nsset->nsproxy)
 310                 free_nsproxy(nsset->nsproxy);
 311 }
 312
 313 static int prepare_nsset(unsigned flags, struct nsset *nsset)
 314 {
 315         struct task_struct *me = current;
 316
 317         nsset->nsproxy = create_new_namespaces(0, me, current_user_ns(), me->fs);
 318         if (IS_ERR(nsset->nsproxy))
 319                 return PTR_ERR(nsset->nsproxy);
 320
 321         if (flags & CLONE_NEWUSER)
 322                 nsset->cred = prepare_creds();
 323         else
 324                 nsset->cred = current_cred();
 325         if (!nsset->cred)
 326                 goto out;
 327
 328         /* Only create a temporary copy of fs_struct if we really need to. */
 329         if (flags == CLONE_NEWNS) {
 330                 nsset->fs = me->fs;
 331         } else if (flags & CLONE_NEWNS) {
 332                 nsset->fs = copy_fs_struct(me->fs);
 333                 if (!nsset->fs)
 334                         goto out;
 335         }
 336
 337         nsset->flags = flags;
 338         return 0;
 339
 340 out:
 341         put_nsset(nsset);
 342         return -ENOMEM;
 343 }
 344
 345 static inline int validate_ns(struct nsset *nsset, struct ns_common *ns)
 346 {
 347         return ns->ops->install(nsset, ns);
 348 }
 349
 350 /*
 351  * This is the inverse operation to unshare().
 352  * Ordering is equivalent to the standard ordering used everywhere else
 353  * during unshare and process creation. The switch to the new set of
 354  * namespaces occurs at the point of no return after installation of
 355  * all requested namespaces was successful in commit_nsset().
 356  */
 357 static int validate_nsset(struct nsset *nsset, struct pid *pid)
 358 {
 359         int ret = 0;
 360         unsigned flags = nsset->flags;
 361         struct user_namespace *user_ns = NULL;
 362         struct pid_namespace *pid_ns = NULL;
 363         struct nsproxy *nsp;
 364         struct task_struct *tsk;
 365
 366         /* Take a "snapshot" of the target task's namespaces. */
 367         rcu_read_lock();
 368         tsk = pid_task(pid, PIDTYPE_PID);
 369         if (!tsk) {
 370                 rcu_read_unlock();
 371                 return -ESRCH;
 372         }
 373
 374         if (!ptrace_may_access(tsk, PTRACE_MODE_READ_REALCREDS)) {
 375                 rcu_read_unlock();
 376                 return -EPERM;
 377         }
 378
 379         task_lock(tsk);
 380         nsp = tsk->nsproxy;
 381         if (nsp)
 382                 get_nsproxy(nsp);
 383         task_unlock(tsk);
 384         if (!nsp) {
 385                 rcu_read_unlock();
 386                 return -ESRCH;
 387         }
 388
 389 #ifdef CONFIG_PID_NS
 390         if (flags & CLONE_NEWPID) {
 391                 pid_ns = task_active_pid_ns(tsk);
 392                 if (unlikely(!pid_ns)) {
 393                         rcu_read_unlock();
 394                         ret = -ESRCH;
 395                         goto out;
 396                 }
 397                 get_pid_ns(pid_ns);
 398         }
 399 #endif
 400
 401 #ifdef CONFIG_USER_NS
 402         if (flags & CLONE_NEWUSER)
 403                 user_ns = get_user_ns(__task_cred(tsk)->user_ns);
 404 #endif
 405         rcu_read_unlock();
 406
 407         /*
 408          * Install requested namespaces. The caller will have
 409          * verified earlier that the requested namespaces are
 410          * supported on this kernel. We don't report errors here
 411          * if a namespace is requested that isn't supported.
 412          */
 413 #ifdef CONFIG_USER_NS
 414         if (flags & CLONE_NEWUSER) {
 415                 ret = validate_ns(nsset, &user_ns->ns);
 416                 if (ret)
 417                         goto out;
 418         }
 419 #endif
 420
 421         if (flags & CLONE_NEWNS) {
 422                 ret = validate_ns(nsset, from_mnt_ns(nsp->mnt_ns));
 423                 if (ret)
 424                         goto out;
 425         }
 426
 427 #ifdef CONFIG_UTS_NS
 428         if (flags & CLONE_NEWUTS) {
 429                 ret = validate_ns(nsset, &nsp->uts_ns->ns);
 430                 if (ret)
 431                         goto out;
 432         }
 433 #endif
 434
 435 #ifdef CONFIG_IPC_NS
 436         if (flags & CLONE_NEWIPC) {
 437                 ret = validate_ns(nsset, &nsp->ipc_ns->ns);
 438                 if (ret)
 439                         goto out;
 440         }
 441 #endif
 442
 443 #ifdef CONFIG_PID_NS
 444         if (flags & CLONE_NEWPID) {
 445                 ret = validate_ns(nsset, &pid_ns->ns);
 446                 if (ret)
 447                         goto out;
 448         }
 449 #endif
 450
 451 #ifdef CONFIG_CGROUPS
 452         if (flags & CLONE_NEWCGROUP) {
 453                 ret = validate_ns(nsset, &nsp->cgroup_ns->ns);
 454                 if (ret)
 455                         goto out;
 456         }
 457 #endif
 458
 459 #ifdef CONFIG_NET_NS
 460         if (flags & CLONE_NEWNET) {
 461                 ret = validate_ns(nsset, &nsp->net_ns->ns);
 462                 if (ret)
 463                         goto out;
 464         }
 465 #endif
 466
 467 out:
 468         if (pid_ns)
 469                 put_pid_ns(pid_ns);
 470         if (nsp)
 471                 put_nsproxy(nsp);
 472         put_user_ns(user_ns);
 473
 474         return ret;
 475 }
 476
 477 /*
 478  * This is the point of no return. There are just a few namespaces
 479  * that do some actual work here and it's sufficiently minimal that
 480  * a separate ns_common operation seems unnecessary for now.
 481  * Unshare is doing the same thing. If we'll end up needing to do
 482  * more in a given namespace or a helper here is ultimately not
 483  * exported anymore a simple commit handler for each namespace
 484  * should be added to ns_common.
 485  */
 486 static void commit_nsset(struct nsset *nsset)
 487 {
 488         unsigned flags = nsset->flags;
 489         struct task_struct *me = current;
 490
 491 #ifdef CONFIG_USER_NS
 492         if (flags & CLONE_NEWUSER) {
 493                 /* transfer ownership */
 494                 commit_creds(nsset_cred(nsset));
 495                 nsset->cred = NULL;
 496         }
 497 #endif
 498
 499         /* We only need to commit if we have used a temporary fs_struct. */
 500         if ((flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS)) {
 501                 set_fs_root(me->fs, &nsset->fs->root);
 502                 set_fs_pwd(me->fs, &nsset->fs->pwd);
 503         }
 504
 505 #ifdef CONFIG_IPC_NS
 506         if (flags & CLONE_NEWIPC)
 507                 exit_sem(me);
 508 #endif
 509
 510         /* transfer ownership */
 511         switch_task_namespaces(me, nsset->nsproxy);
 512         nsset->nsproxy = NULL;
 513 }
 514
 515 SYSCALL_DEFINE2(setns, int, fd, int, flags)
 516 {
 517         struct file *file;
 518         struct ns_common *ns = NULL;
 519         struct nsset nsset = {};
 520         int err = 0;
 521
 522         file = fget(fd);
 523         if (!file)
 524                 return -EBADF;
 525
 526         if (proc_ns_file(file)) {
 527                 ns = get_proc_ns(file_inode(file));
 528                 if (flags && (ns->ops->type != flags))
 529                         err = -EINVAL;
 530                 flags = ns->ops->type;
 531         } else if (!IS_ERR(pidfd_pid(file))) {
 532                 err = check_setns_flags(flags);
 533         } else {
 534                 err = -EBADF;
 535         }
 536         if (err)
 537                 goto out;
 538
 539         err = prepare_nsset(flags, &nsset);
 540         if (err)
 541                 goto out;
 542
 543         if (proc_ns_file(file))
 544                 err = validate_ns(&nsset, ns);
 545         else
 546                 err = validate_nsset(&nsset, file->private_data);
 547         if (!err) {
 548                 commit_nsset(&nsset);
 549                 perf_event_namespaces(current);
 550         }
 551         put_nsset(&nsset);
 552 out:
 553         fput(file);
 554         return err;
 555 }
 556
 557 int __init nsproxy_cache_init(void)
 558 {
 559         nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
 560         return 0;
 561 }