linux/kernel/user_namespace.c
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   1/*
   2 *  This program is free software; you can redistribute it and/or
   3 *  modify it under the terms of the GNU General Public License as
   4 *  published by the Free Software Foundation, version 2 of the
   5 *  License.
   6 */
   7
   8#include <linux/export.h>
   9#include <linux/nsproxy.h>
  10#include <linux/slab.h>
  11#include <linux/user_namespace.h>
  12#include <linux/proc_ns.h>
  13#include <linux/highuid.h>
  14#include <linux/cred.h>
  15#include <linux/securebits.h>
  16#include <linux/keyctl.h>
  17#include <linux/key-type.h>
  18#include <keys/user-type.h>
  19#include <linux/seq_file.h>
  20#include <linux/fs.h>
  21#include <linux/uaccess.h>
  22#include <linux/ctype.h>
  23#include <linux/projid.h>
  24#include <linux/fs_struct.h>
  25
  26static struct kmem_cache *user_ns_cachep __read_mostly;
  27
  28static bool new_idmap_permitted(const struct file *file,
  29                                struct user_namespace *ns, int cap_setid,
  30                                struct uid_gid_map *map);
  31
  32static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
  33{
  34        /* Start with the same capabilities as init but useless for doing
  35         * anything as the capabilities are bound to the new user namespace.
  36         */
  37        cred->securebits = SECUREBITS_DEFAULT;
  38        cred->cap_inheritable = CAP_EMPTY_SET;
  39        cred->cap_permitted = CAP_FULL_SET;
  40        cred->cap_effective = CAP_FULL_SET;
  41        cred->cap_bset = CAP_FULL_SET;
  42#ifdef CONFIG_KEYS
  43        key_put(cred->request_key_auth);
  44        cred->request_key_auth = NULL;
  45#endif
  46        /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
  47        cred->user_ns = user_ns;
  48}
  49
  50/*
  51 * Create a new user namespace, deriving the creator from the user in the
  52 * passed credentials, and replacing that user with the new root user for the
  53 * new namespace.
  54 *
  55 * This is called by copy_creds(), which will finish setting the target task's
  56 * credentials.
  57 */
  58int create_user_ns(struct cred *new)
  59{
  60        struct user_namespace *ns, *parent_ns = new->user_ns;
  61        kuid_t owner = new->euid;
  62        kgid_t group = new->egid;
  63        int ret;
  64
  65        if (parent_ns->level > 32)
  66                return -EUSERS;
  67
  68        /*
  69         * Verify that we can not violate the policy of which files
  70         * may be accessed that is specified by the root directory,
  71         * by verifing that the root directory is at the root of the
  72         * mount namespace which allows all files to be accessed.
  73         */
  74        if (current_chrooted())
  75                return -EPERM;
  76
  77        /* The creator needs a mapping in the parent user namespace
  78         * or else we won't be able to reasonably tell userspace who
  79         * created a user_namespace.
  80         */
  81        if (!kuid_has_mapping(parent_ns, owner) ||
  82            !kgid_has_mapping(parent_ns, group))
  83                return -EPERM;
  84
  85        ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
  86        if (!ns)
  87                return -ENOMEM;
  88
  89        ret = proc_alloc_inum(&ns->proc_inum);
  90        if (ret) {
  91                kmem_cache_free(user_ns_cachep, ns);
  92                return ret;
  93        }
  94
  95        atomic_set(&ns->count, 1);
  96        /* Leave the new->user_ns reference with the new user namespace. */
  97        ns->parent = parent_ns;
  98        ns->level = parent_ns->level + 1;
  99        ns->owner = owner;
 100        ns->group = group;
 101
 102        set_cred_user_ns(new, ns);
 103
 104        return 0;
 105}
 106
 107int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
 108{
 109        struct cred *cred;
 110        int err = -ENOMEM;
 111
 112        if (!(unshare_flags & CLONE_NEWUSER))
 113                return 0;
 114
 115        cred = prepare_creds();
 116        if (cred) {
 117                err = create_user_ns(cred);
 118                if (err)
 119                        put_cred(cred);
 120                else
 121                        *new_cred = cred;
 122        }
 123
 124        return err;
 125}
 126
 127void free_user_ns(struct user_namespace *ns)
 128{
 129        struct user_namespace *parent;
 130
 131        do {
 132                parent = ns->parent;
 133                proc_free_inum(ns->proc_inum);
 134                kmem_cache_free(user_ns_cachep, ns);
 135                ns = parent;
 136        } while (atomic_dec_and_test(&parent->count));
 137}
 138EXPORT_SYMBOL(free_user_ns);
 139
 140static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
 141{
 142        unsigned idx, extents;
 143        u32 first, last, id2;
 144
 145        id2 = id + count - 1;
 146
 147        /* Find the matching extent */
 148        extents = map->nr_extents;
 149        smp_read_barrier_depends();
 150        for (idx = 0; idx < extents; idx++) {
 151                first = map->extent[idx].first;
 152                last = first + map->extent[idx].count - 1;
 153                if (id >= first && id <= last &&
 154                    (id2 >= first && id2 <= last))
 155                        break;
 156        }
 157        /* Map the id or note failure */
 158        if (idx < extents)
 159                id = (id - first) + map->extent[idx].lower_first;
 160        else
 161                id = (u32) -1;
 162
 163        return id;
 164}
 165
 166static u32 map_id_down(struct uid_gid_map *map, u32 id)
 167{
 168        unsigned idx, extents;
 169        u32 first, last;
 170
 171        /* Find the matching extent */
 172        extents = map->nr_extents;
 173        smp_read_barrier_depends();
 174        for (idx = 0; idx < extents; idx++) {
 175                first = map->extent[idx].first;
 176                last = first + map->extent[idx].count - 1;
 177                if (id >= first && id <= last)
 178                        break;
 179        }
 180        /* Map the id or note failure */
 181        if (idx < extents)
 182                id = (id - first) + map->extent[idx].lower_first;
 183        else
 184                id = (u32) -1;
 185
 186        return id;
 187}
 188
 189static u32 map_id_up(struct uid_gid_map *map, u32 id)
 190{
 191        unsigned idx, extents;
 192        u32 first, last;
 193
 194        /* Find the matching extent */
 195        extents = map->nr_extents;
 196        smp_read_barrier_depends();
 197        for (idx = 0; idx < extents; idx++) {
 198                first = map->extent[idx].lower_first;
 199                last = first + map->extent[idx].count - 1;
 200                if (id >= first && id <= last)
 201                        break;
 202        }
 203        /* Map the id or note failure */
 204        if (idx < extents)
 205                id = (id - first) + map->extent[idx].first;
 206        else
 207                id = (u32) -1;
 208
 209        return id;
 210}
 211
 212/**
 213 *      make_kuid - Map a user-namespace uid pair into a kuid.
 214 *      @ns:  User namespace that the uid is in
 215 *      @uid: User identifier
 216 *
 217 *      Maps a user-namespace uid pair into a kernel internal kuid,
 218 *      and returns that kuid.
 219 *
 220 *      When there is no mapping defined for the user-namespace uid
 221 *      pair INVALID_UID is returned.  Callers are expected to test
 222 *      for and handle handle INVALID_UID being returned.  INVALID_UID
 223 *      may be tested for using uid_valid().
 224 */
 225kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
 226{
 227        /* Map the uid to a global kernel uid */
 228        return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
 229}
 230EXPORT_SYMBOL(make_kuid);
 231
 232/**
 233 *      from_kuid - Create a uid from a kuid user-namespace pair.
 234 *      @targ: The user namespace we want a uid in.
 235 *      @kuid: The kernel internal uid to start with.
 236 *
 237 *      Map @kuid into the user-namespace specified by @targ and
 238 *      return the resulting uid.
 239 *
 240 *      There is always a mapping into the initial user_namespace.
 241 *
 242 *      If @kuid has no mapping in @targ (uid_t)-1 is returned.
 243 */
 244uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
 245{
 246        /* Map the uid from a global kernel uid */
 247        return map_id_up(&targ->uid_map, __kuid_val(kuid));
 248}
 249EXPORT_SYMBOL(from_kuid);
 250
 251/**
 252 *      from_kuid_munged - Create a uid from a kuid user-namespace pair.
 253 *      @targ: The user namespace we want a uid in.
 254 *      @kuid: The kernel internal uid to start with.
 255 *
 256 *      Map @kuid into the user-namespace specified by @targ and
 257 *      return the resulting uid.
 258 *
 259 *      There is always a mapping into the initial user_namespace.
 260 *
 261 *      Unlike from_kuid from_kuid_munged never fails and always
 262 *      returns a valid uid.  This makes from_kuid_munged appropriate
 263 *      for use in syscalls like stat and getuid where failing the
 264 *      system call and failing to provide a valid uid are not an
 265 *      options.
 266 *
 267 *      If @kuid has no mapping in @targ overflowuid is returned.
 268 */
 269uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
 270{
 271        uid_t uid;
 272        uid = from_kuid(targ, kuid);
 273
 274        if (uid == (uid_t) -1)
 275                uid = overflowuid;
 276        return uid;
 277}
 278EXPORT_SYMBOL(from_kuid_munged);
 279
 280/**
 281 *      make_kgid - Map a user-namespace gid pair into a kgid.
 282 *      @ns:  User namespace that the gid is in
 283 *      @uid: group identifier
 284 *
 285 *      Maps a user-namespace gid pair into a kernel internal kgid,
 286 *      and returns that kgid.
 287 *
 288 *      When there is no mapping defined for the user-namespace gid
 289 *      pair INVALID_GID is returned.  Callers are expected to test
 290 *      for and handle INVALID_GID being returned.  INVALID_GID may be
 291 *      tested for using gid_valid().
 292 */
 293kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
 294{
 295        /* Map the gid to a global kernel gid */
 296        return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
 297}
 298EXPORT_SYMBOL(make_kgid);
 299
 300/**
 301 *      from_kgid - Create a gid from a kgid user-namespace pair.
 302 *      @targ: The user namespace we want a gid in.
 303 *      @kgid: The kernel internal gid to start with.
 304 *
 305 *      Map @kgid into the user-namespace specified by @targ and
 306 *      return the resulting gid.
 307 *
 308 *      There is always a mapping into the initial user_namespace.
 309 *
 310 *      If @kgid has no mapping in @targ (gid_t)-1 is returned.
 311 */
 312gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
 313{
 314        /* Map the gid from a global kernel gid */
 315        return map_id_up(&targ->gid_map, __kgid_val(kgid));
 316}
 317EXPORT_SYMBOL(from_kgid);
 318
 319/**
 320 *      from_kgid_munged - Create a gid from a kgid user-namespace pair.
 321 *      @targ: The user namespace we want a gid in.
 322 *      @kgid: The kernel internal gid to start with.
 323 *
 324 *      Map @kgid into the user-namespace specified by @targ and
 325 *      return the resulting gid.
 326 *
 327 *      There is always a mapping into the initial user_namespace.
 328 *
 329 *      Unlike from_kgid from_kgid_munged never fails and always
 330 *      returns a valid gid.  This makes from_kgid_munged appropriate
 331 *      for use in syscalls like stat and getgid where failing the
 332 *      system call and failing to provide a valid gid are not options.
 333 *
 334 *      If @kgid has no mapping in @targ overflowgid is returned.
 335 */
 336gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
 337{
 338        gid_t gid;
 339        gid = from_kgid(targ, kgid);
 340
 341        if (gid == (gid_t) -1)
 342                gid = overflowgid;
 343        return gid;
 344}
 345EXPORT_SYMBOL(from_kgid_munged);
 346
 347/**
 348 *      make_kprojid - Map a user-namespace projid pair into a kprojid.
 349 *      @ns:  User namespace that the projid is in
 350 *      @projid: Project identifier
 351 *
 352 *      Maps a user-namespace uid pair into a kernel internal kuid,
 353 *      and returns that kuid.
 354 *
 355 *      When there is no mapping defined for the user-namespace projid
 356 *      pair INVALID_PROJID is returned.  Callers are expected to test
 357 *      for and handle handle INVALID_PROJID being returned.  INVALID_PROJID
 358 *      may be tested for using projid_valid().
 359 */
 360kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
 361{
 362        /* Map the uid to a global kernel uid */
 363        return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
 364}
 365EXPORT_SYMBOL(make_kprojid);
 366
 367/**
 368 *      from_kprojid - Create a projid from a kprojid user-namespace pair.
 369 *      @targ: The user namespace we want a projid in.
 370 *      @kprojid: The kernel internal project identifier to start with.
 371 *
 372 *      Map @kprojid into the user-namespace specified by @targ and
 373 *      return the resulting projid.
 374 *
 375 *      There is always a mapping into the initial user_namespace.
 376 *
 377 *      If @kprojid has no mapping in @targ (projid_t)-1 is returned.
 378 */
 379projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
 380{
 381        /* Map the uid from a global kernel uid */
 382        return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
 383}
 384EXPORT_SYMBOL(from_kprojid);
 385
 386/**
 387 *      from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
 388 *      @targ: The user namespace we want a projid in.
 389 *      @kprojid: The kernel internal projid to start with.
 390 *
 391 *      Map @kprojid into the user-namespace specified by @targ and
 392 *      return the resulting projid.
 393 *
 394 *      There is always a mapping into the initial user_namespace.
 395 *
 396 *      Unlike from_kprojid from_kprojid_munged never fails and always
 397 *      returns a valid projid.  This makes from_kprojid_munged
 398 *      appropriate for use in syscalls like stat and where
 399 *      failing the system call and failing to provide a valid projid are
 400 *      not an options.
 401 *
 402 *      If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
 403 */
 404projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
 405{
 406        projid_t projid;
 407        projid = from_kprojid(targ, kprojid);
 408
 409        if (projid == (projid_t) -1)
 410                projid = OVERFLOW_PROJID;
 411        return projid;
 412}
 413EXPORT_SYMBOL(from_kprojid_munged);
 414
 415
 416static int uid_m_show(struct seq_file *seq, void *v)
 417{
 418        struct user_namespace *ns = seq->private;
 419        struct uid_gid_extent *extent = v;
 420        struct user_namespace *lower_ns;
 421        uid_t lower;
 422
 423        lower_ns = seq_user_ns(seq);
 424        if ((lower_ns == ns) && lower_ns->parent)
 425                lower_ns = lower_ns->parent;
 426
 427        lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
 428
 429        seq_printf(seq, "%10u %10u %10u\n",
 430                extent->first,
 431                lower,
 432                extent->count);
 433
 434        return 0;
 435}
 436
 437static int gid_m_show(struct seq_file *seq, void *v)
 438{
 439        struct user_namespace *ns = seq->private;
 440        struct uid_gid_extent *extent = v;
 441        struct user_namespace *lower_ns;
 442        gid_t lower;
 443
 444        lower_ns = seq_user_ns(seq);
 445        if ((lower_ns == ns) && lower_ns->parent)
 446                lower_ns = lower_ns->parent;
 447
 448        lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
 449
 450        seq_printf(seq, "%10u %10u %10u\n",
 451                extent->first,
 452                lower,
 453                extent->count);
 454
 455        return 0;
 456}
 457
 458static int projid_m_show(struct seq_file *seq, void *v)
 459{
 460        struct user_namespace *ns = seq->private;
 461        struct uid_gid_extent *extent = v;
 462        struct user_namespace *lower_ns;
 463        projid_t lower;
 464
 465        lower_ns = seq_user_ns(seq);
 466        if ((lower_ns == ns) && lower_ns->parent)
 467                lower_ns = lower_ns->parent;
 468
 469        lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
 470
 471        seq_printf(seq, "%10u %10u %10u\n",
 472                extent->first,
 473                lower,
 474                extent->count);
 475
 476        return 0;
 477}
 478
 479static void *m_start(struct seq_file *seq, loff_t *ppos, struct uid_gid_map *map)
 480{
 481        struct uid_gid_extent *extent = NULL;
 482        loff_t pos = *ppos;
 483
 484        if (pos < map->nr_extents)
 485                extent = &map->extent[pos];
 486
 487        return extent;
 488}
 489
 490static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
 491{
 492        struct user_namespace *ns = seq->private;
 493
 494        return m_start(seq, ppos, &ns->uid_map);
 495}
 496
 497static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
 498{
 499        struct user_namespace *ns = seq->private;
 500
 501        return m_start(seq, ppos, &ns->gid_map);
 502}
 503
 504static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
 505{
 506        struct user_namespace *ns = seq->private;
 507
 508        return m_start(seq, ppos, &ns->projid_map);
 509}
 510
 511static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
 512{
 513        (*pos)++;
 514        return seq->op->start(seq, pos);
 515}
 516
 517static void m_stop(struct seq_file *seq, void *v)
 518{
 519        return;
 520}
 521
 522struct seq_operations proc_uid_seq_operations = {
 523        .start = uid_m_start,
 524        .stop = m_stop,
 525        .next = m_next,
 526        .show = uid_m_show,
 527};
 528
 529struct seq_operations proc_gid_seq_operations = {
 530        .start = gid_m_start,
 531        .stop = m_stop,
 532        .next = m_next,
 533        .show = gid_m_show,
 534};
 535
 536struct seq_operations proc_projid_seq_operations = {
 537        .start = projid_m_start,
 538        .stop = m_stop,
 539        .next = m_next,
 540        .show = projid_m_show,
 541};
 542
 543static bool mappings_overlap(struct uid_gid_map *new_map, struct uid_gid_extent *extent)
 544{
 545        u32 upper_first, lower_first, upper_last, lower_last;
 546        unsigned idx;
 547
 548        upper_first = extent->first;
 549        lower_first = extent->lower_first;
 550        upper_last = upper_first + extent->count - 1;
 551        lower_last = lower_first + extent->count - 1;
 552
 553        for (idx = 0; idx < new_map->nr_extents; idx++) {
 554                u32 prev_upper_first, prev_lower_first;
 555                u32 prev_upper_last, prev_lower_last;
 556                struct uid_gid_extent *prev;
 557
 558                prev = &new_map->extent[idx];
 559
 560                prev_upper_first = prev->first;
 561                prev_lower_first = prev->lower_first;
 562                prev_upper_last = prev_upper_first + prev->count - 1;
 563                prev_lower_last = prev_lower_first + prev->count - 1;
 564
 565                /* Does the upper range intersect a previous extent? */
 566                if ((prev_upper_first <= upper_last) &&
 567                    (prev_upper_last >= upper_first))
 568                        return true;
 569
 570                /* Does the lower range intersect a previous extent? */
 571                if ((prev_lower_first <= lower_last) &&
 572                    (prev_lower_last >= lower_first))
 573                        return true;
 574        }
 575        return false;
 576}
 577
 578
 579static DEFINE_MUTEX(id_map_mutex);
 580
 581static ssize_t map_write(struct file *file, const char __user *buf,
 582                         size_t count, loff_t *ppos,
 583                         int cap_setid,
 584                         struct uid_gid_map *map,
 585                         struct uid_gid_map *parent_map)
 586{
 587        struct seq_file *seq = file->private_data;
 588        struct user_namespace *ns = seq->private;
 589        struct uid_gid_map new_map;
 590        unsigned idx;
 591        struct uid_gid_extent *extent = NULL;
 592        unsigned long page = 0;
 593        char *kbuf, *pos, *next_line;
 594        ssize_t ret = -EINVAL;
 595
 596        /*
 597         * The id_map_mutex serializes all writes to any given map.
 598         *
 599         * Any map is only ever written once.
 600         *
 601         * An id map fits within 1 cache line on most architectures.
 602         *
 603         * On read nothing needs to be done unless you are on an
 604         * architecture with a crazy cache coherency model like alpha.
 605         *
 606         * There is a one time data dependency between reading the
 607         * count of the extents and the values of the extents.  The
 608         * desired behavior is to see the values of the extents that
 609         * were written before the count of the extents.
 610         *
 611         * To achieve this smp_wmb() is used on guarantee the write
 612         * order and smp_read_barrier_depends() is guaranteed that we
 613         * don't have crazy architectures returning stale data.
 614         *
 615         */
 616        mutex_lock(&id_map_mutex);
 617
 618        ret = -EPERM;
 619        /* Only allow one successful write to the map */
 620        if (map->nr_extents != 0)
 621                goto out;
 622
 623        /*
 624         * Adjusting namespace settings requires capabilities on the target.
 625         */
 626        if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
 627                goto out;
 628
 629        /* Get a buffer */
 630        ret = -ENOMEM;
 631        page = __get_free_page(GFP_TEMPORARY);
 632        kbuf = (char *) page;
 633        if (!page)
 634                goto out;
 635
 636        /* Only allow <= page size writes at the beginning of the file */
 637        ret = -EINVAL;
 638        if ((*ppos != 0) || (count >= PAGE_SIZE))
 639                goto out;
 640
 641        /* Slurp in the user data */
 642        ret = -EFAULT;
 643        if (copy_from_user(kbuf, buf, count))
 644                goto out;
 645        kbuf[count] = '\0';
 646
 647        /* Parse the user data */
 648        ret = -EINVAL;
 649        pos = kbuf;
 650        new_map.nr_extents = 0;
 651        for (;pos; pos = next_line) {
 652                extent = &new_map.extent[new_map.nr_extents];
 653
 654                /* Find the end of line and ensure I don't look past it */
 655                next_line = strchr(pos, '\n');
 656                if (next_line) {
 657                        *next_line = '\0';
 658                        next_line++;
 659                        if (*next_line == '\0')
 660                                next_line = NULL;
 661                }
 662
 663                pos = skip_spaces(pos);
 664                extent->first = simple_strtoul(pos, &pos, 10);
 665                if (!isspace(*pos))
 666                        goto out;
 667
 668                pos = skip_spaces(pos);
 669                extent->lower_first = simple_strtoul(pos, &pos, 10);
 670                if (!isspace(*pos))
 671                        goto out;
 672
 673                pos = skip_spaces(pos);
 674                extent->count = simple_strtoul(pos, &pos, 10);
 675                if (*pos && !isspace(*pos))
 676                        goto out;
 677
 678                /* Verify there is not trailing junk on the line */
 679                pos = skip_spaces(pos);
 680                if (*pos != '\0')
 681                        goto out;
 682
 683                /* Verify we have been given valid starting values */
 684                if ((extent->first == (u32) -1) ||
 685                    (extent->lower_first == (u32) -1 ))
 686                        goto out;
 687
 688                /* Verify count is not zero and does not cause the extent to wrap */
 689                if ((extent->first + extent->count) <= extent->first)
 690                        goto out;
 691                if ((extent->lower_first + extent->count) <= extent->lower_first)
 692                        goto out;
 693
 694                /* Do the ranges in extent overlap any previous extents? */
 695                if (mappings_overlap(&new_map, extent))
 696                        goto out;
 697
 698                new_map.nr_extents++;
 699
 700                /* Fail if the file contains too many extents */
 701                if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
 702                    (next_line != NULL))
 703                        goto out;
 704        }
 705        /* Be very certaint the new map actually exists */
 706        if (new_map.nr_extents == 0)
 707                goto out;
 708
 709        ret = -EPERM;
 710        /* Validate the user is allowed to use user id's mapped to. */
 711        if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
 712                goto out;
 713
 714        /* Map the lower ids from the parent user namespace to the
 715         * kernel global id space.
 716         */
 717        for (idx = 0; idx < new_map.nr_extents; idx++) {
 718                u32 lower_first;
 719                extent = &new_map.extent[idx];
 720
 721                lower_first = map_id_range_down(parent_map,
 722                                                extent->lower_first,
 723                                                extent->count);
 724
 725                /* Fail if we can not map the specified extent to
 726                 * the kernel global id space.
 727                 */
 728                if (lower_first == (u32) -1)
 729                        goto out;
 730
 731                extent->lower_first = lower_first;
 732        }
 733
 734        /* Install the map */
 735        memcpy(map->extent, new_map.extent,
 736                new_map.nr_extents*sizeof(new_map.extent[0]));
 737        smp_wmb();
 738        map->nr_extents = new_map.nr_extents;
 739
 740        *ppos = count;
 741        ret = count;
 742out:
 743        mutex_unlock(&id_map_mutex);
 744        if (page)
 745                free_page(page);
 746        return ret;
 747}
 748
 749ssize_t proc_uid_map_write(struct file *file, const char __user *buf, size_t size, loff_t *ppos)
 750{
 751        struct seq_file *seq = file->private_data;
 752        struct user_namespace *ns = seq->private;
 753        struct user_namespace *seq_ns = seq_user_ns(seq);
 754
 755        if (!ns->parent)
 756                return -EPERM;
 757
 758        if ((seq_ns != ns) && (seq_ns != ns->parent))
 759                return -EPERM;
 760
 761        return map_write(file, buf, size, ppos, CAP_SETUID,
 762                         &ns->uid_map, &ns->parent->uid_map);
 763}
 764
 765ssize_t proc_gid_map_write(struct file *file, const char __user *buf, size_t size, loff_t *ppos)
 766{
 767        struct seq_file *seq = file->private_data;
 768        struct user_namespace *ns = seq->private;
 769        struct user_namespace *seq_ns = seq_user_ns(seq);
 770
 771        if (!ns->parent)
 772                return -EPERM;
 773
 774        if ((seq_ns != ns) && (seq_ns != ns->parent))
 775                return -EPERM;
 776
 777        return map_write(file, buf, size, ppos, CAP_SETGID,
 778                         &ns->gid_map, &ns->parent->gid_map);
 779}
 780
 781ssize_t proc_projid_map_write(struct file *file, const char __user *buf, size_t size, loff_t *ppos)
 782{
 783        struct seq_file *seq = file->private_data;
 784        struct user_namespace *ns = seq->private;
 785        struct user_namespace *seq_ns = seq_user_ns(seq);
 786
 787        if (!ns->parent)
 788                return -EPERM;
 789
 790        if ((seq_ns != ns) && (seq_ns != ns->parent))
 791                return -EPERM;
 792
 793        /* Anyone can set any valid project id no capability needed */
 794        return map_write(file, buf, size, ppos, -1,
 795                         &ns->projid_map, &ns->parent->projid_map);
 796}
 797
 798static bool new_idmap_permitted(const struct file *file, 
 799                                struct user_namespace *ns, int cap_setid,
 800                                struct uid_gid_map *new_map)
 801{
 802        /* Allow mapping to your own filesystem ids */
 803        if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1)) {
 804                u32 id = new_map->extent[0].lower_first;
 805                if (cap_setid == CAP_SETUID) {
 806                        kuid_t uid = make_kuid(ns->parent, id);
 807                        if (uid_eq(uid, file->f_cred->fsuid))
 808                                return true;
 809                }
 810                else if (cap_setid == CAP_SETGID) {
 811                        kgid_t gid = make_kgid(ns->parent, id);
 812                        if (gid_eq(gid, file->f_cred->fsgid))
 813                                return true;
 814                }
 815        }
 816
 817        /* Allow anyone to set a mapping that doesn't require privilege */
 818        if (!cap_valid(cap_setid))
 819                return true;
 820
 821        /* Allow the specified ids if we have the appropriate capability
 822         * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
 823         * And the opener of the id file also had the approprpiate capability.
 824         */
 825        if (ns_capable(ns->parent, cap_setid) &&
 826            file_ns_capable(file, ns->parent, cap_setid))
 827                return true;
 828
 829        return false;
 830}
 831
 832static void *userns_get(struct task_struct *task)
 833{
 834        struct user_namespace *user_ns;
 835
 836        rcu_read_lock();
 837        user_ns = get_user_ns(__task_cred(task)->user_ns);
 838        rcu_read_unlock();
 839
 840        return user_ns;
 841}
 842
 843static void userns_put(void *ns)
 844{
 845        put_user_ns(ns);
 846}
 847
 848static int userns_install(struct nsproxy *nsproxy, void *ns)
 849{
 850        struct user_namespace *user_ns = ns;
 851        struct cred *cred;
 852
 853        /* Don't allow gaining capabilities by reentering
 854         * the same user namespace.
 855         */
 856        if (user_ns == current_user_ns())
 857                return -EINVAL;
 858
 859        /* Threaded processes may not enter a different user namespace */
 860        if (atomic_read(&current->mm->mm_users) > 1)
 861                return -EINVAL;
 862
 863        if (current->fs->users != 1)
 864                return -EINVAL;
 865
 866        if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 867                return -EPERM;
 868
 869        cred = prepare_creds();
 870        if (!cred)
 871                return -ENOMEM;
 872
 873        put_user_ns(cred->user_ns);
 874        set_cred_user_ns(cred, get_user_ns(user_ns));
 875
 876        return commit_creds(cred);
 877}
 878
 879static unsigned int userns_inum(void *ns)
 880{
 881        struct user_namespace *user_ns = ns;
 882        return user_ns->proc_inum;
 883}
 884
 885const struct proc_ns_operations userns_operations = {
 886        .name           = "user",
 887        .type           = CLONE_NEWUSER,
 888        .get            = userns_get,
 889        .put            = userns_put,
 890        .install        = userns_install,
 891        .inum           = userns_inum,
 892};
 893
 894static __init int user_namespaces_init(void)
 895{
 896        user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
 897        return 0;
 898}
 899module_init(user_namespaces_init);
 900
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