OSCL-LXR linux-6.0.1/​kernel/​user_namespace.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 
 #include <linux/export.h>
 #include <linux/nsproxy.h>
 #include <linux/slab.h>
 #include <linux/sched/signal.h>
 #include <linux/user_namespace.h>
 #include <linux/proc_ns.h>
 #include <linux/highuid.h>
 #include <linux/cred.h>
 #include <linux/securebits.h>
 #include <linux/keyctl.h>
 #include <linux/key-type.h>
 #include <keys/user-type.h>
 #include <linux/seq_file.h>
 #include <linux/fs.h>
 #include <linux/uaccess.h>
 #include <linux/ctype.h>
 #include <linux/projid.h>
 #include <linux/fs_struct.h>
 #include <linux/bsearch.h>
 #include <linux/sort.h>
 
 static struct kmem_cache *user_ns_cachep __read_mostly;
 static DEFINE_MUTEX(userns_state_mutex);
 
 static bool new_idmap_permitted(const struct file *file,
                 struct user_namespace *ns, int cap_setid,
                 struct uid_gid_map *map);
 static void free_user_ns(struct work_struct *work);
 
 static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
 {
     return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
 }
 
 static void dec_user_namespaces(struct ucounts *ucounts)
 {
     return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
 }
 
 static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
 {
     /* Start with the same capabilities as init but useless for doing
      * anything as the capabilities are bound to the new user namespace.
      */
     cred->securebits = SECUREBITS_DEFAULT;
     cred->cap_inheritable = CAP_EMPTY_SET;
     cred->cap_permitted = CAP_FULL_SET;
     cred->cap_effective = CAP_FULL_SET;
     cred->cap_ambient = CAP_EMPTY_SET;
     cred->cap_bset = CAP_FULL_SET;
 #ifdef CONFIG_KEYS
     key_put(cred->request_key_auth);
     cred->request_key_auth = NULL;
 #endif
     /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
     cred->user_ns = user_ns;
 }
 
 static unsigned long enforced_nproc_rlimit(void)
 {
     unsigned long limit = RLIM_INFINITY;
 
     /* Is RLIMIT_NPROC currently enforced? */
     if (!uid_eq(current_uid(), GLOBAL_ROOT_UID) ||
         (current_user_ns() != &init_user_ns))
         limit = rlimit(RLIMIT_NPROC);
 
     return limit;
 }
 
 /*
  * Create a new user namespace, deriving the creator from the user in the
  * passed credentials, and replacing that user with the new root user for the
  * new namespace.
  *
  * This is called by copy_creds(), which will finish setting the target task's
  * credentials.
  */
 int create_user_ns(struct cred *new)
 {
     struct user_namespace *ns, *parent_ns = new->user_ns;
     kuid_t owner = new->euid;
     kgid_t group = new->egid;
     struct ucounts *ucounts;
     int ret, i;
 
     ret = -ENOSPC;
     if (parent_ns->level > 32)
         goto fail;
 
     ucounts = inc_user_namespaces(parent_ns, owner);
     if (!ucounts)
         goto fail;
 
     /*
      * Verify that we can not violate the policy of which files
      * may be accessed that is specified by the root directory,
      * by verifying that the root directory is at the root of the
      * mount namespace which allows all files to be accessed.
      */
     ret = -EPERM;
     if (current_chrooted())
         goto fail_dec;
 
     /* The creator needs a mapping in the parent user namespace
      * or else we won't be able to reasonably tell userspace who
      * created a user_namespace.
      */
     ret = -EPERM;
     if (!kuid_has_mapping(parent_ns, owner) ||
         !kgid_has_mapping(parent_ns, group))
         goto fail_dec;
 
     ret = -ENOMEM;
     ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
     if (!ns)
         goto fail_dec;
 
     ns->parent_could_setfcap = cap_raised(new->cap_effective, CAP_SETFCAP);
     ret = ns_alloc_inum(&ns->ns);
     if (ret)
         goto fail_free;
     ns->ns.ops = &userns_operations;
 
     refcount_set(&ns->ns.count, 1);
     /* Leave the new->user_ns reference with the new user namespace. */
     ns->parent = parent_ns;
     ns->level = parent_ns->level + 1;
     ns->owner = owner;
     ns->group = group;
     INIT_WORK(&ns->work, free_user_ns);
     for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++) {
         ns->ucount_max[i] = INT_MAX;
     }
     set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_NPROC, enforced_nproc_rlimit());
     set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
     set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING));
     set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK));
     ns->ucounts = ucounts;
 
     /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
     mutex_lock(&userns_state_mutex);
     ns->flags = parent_ns->flags;
     mutex_unlock(&userns_state_mutex);
 
 #ifdef CONFIG_KEYS
     INIT_LIST_HEAD(&ns->keyring_name_list);
     init_rwsem(&ns->keyring_sem);
 #endif
     ret = -ENOMEM;
     if (!setup_userns_sysctls(ns))
         goto fail_keyring;
 
     set_cred_user_ns(new, ns);
     return 0;
 fail_keyring:
 #ifdef CONFIG_PERSISTENT_KEYRINGS
     key_put(ns->persistent_keyring_register);
 #endif
     ns_free_inum(&ns->ns);
 fail_free:
     kmem_cache_free(user_ns_cachep, ns);
 fail_dec:
     dec_user_namespaces(ucounts);
 fail:
     return ret;
 }
 
 int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
 {
     struct cred *cred;
     int err = -ENOMEM;
 
     if (!(unshare_flags & CLONE_NEWUSER))
         return 0;
 
     cred = prepare_creds();
     if (cred) {
         err = create_user_ns(cred);
         if (err)
             put_cred(cred);
         else
             *new_cred = cred;
     }
 
     return err;
 }
 
 static void free_user_ns(struct work_struct *work)
 {
     struct user_namespace *parent, *ns =
         container_of(work, struct user_namespace, work);
 
     do {
         struct ucounts *ucounts = ns->ucounts;
         parent = ns->parent;
         if (ns->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
             kfree(ns->gid_map.forward);
             kfree(ns->gid_map.reverse);
         }
         if (ns->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
             kfree(ns->uid_map.forward);
             kfree(ns->uid_map.reverse);
         }
         if (ns->projid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
             kfree(ns->projid_map.forward);
             kfree(ns->projid_map.reverse);
         }
         retire_userns_sysctls(ns);
         key_free_user_ns(ns);
         ns_free_inum(&ns->ns);
         kmem_cache_free(user_ns_cachep, ns);
         dec_user_namespaces(ucounts);
         ns = parent;
     } while (refcount_dec_and_test(&parent->ns.count));
 }
 
 void __put_user_ns(struct user_namespace *ns)
 {
     schedule_work(&ns->work);
 }
 EXPORT_SYMBOL(__put_user_ns);
 
 /**
  * idmap_key struct holds the information necessary to find an idmapping in a
  * sorted idmap array. It is passed to cmp_map_id() as first argument.
  */
 struct idmap_key {
     bool map_up; /* true  -> id from kid; false -> kid from id */
     u32 id; /* id to find */
     u32 count; /* == 0 unless used with map_id_range_down() */
 };
 
 /**
  * cmp_map_id - Function to be passed to bsearch() to find the requested
  * idmapping. Expects struct idmap_key to be passed via @k.
  */
 static int cmp_map_id(const void *k, const void *e)
 {
     u32 first, last, id2;
     const struct idmap_key *key = k;
     const struct uid_gid_extent *el = e;
 
     id2 = key->id + key->count - 1;
 
     /* handle map_id_{down,up}() */
     if (key->map_up)
         first = el->lower_first;
     else
         first = el->first;
 
     last = first + el->count - 1;
 
     if (key->id >= first && key->id <= last &&
         (id2 >= first && id2 <= last))
         return 0;
 
     if (key->id < first || id2 < first)
         return -1;
 
     return 1;
 }
 
 /**
  * map_id_range_down_max - Find idmap via binary search in ordered idmap array.
  * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
  */
 static struct uid_gid_extent *
 map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
 {
     struct idmap_key key;
 
     key.map_up = false;
     key.count = count;
     key.id = id;
 
     return bsearch(&key, map->forward, extents,
                sizeof(struct uid_gid_extent), cmp_map_id);
 }
 
 /**
  * map_id_range_down_base - Find idmap via binary search in static extent array.
  * Can only be called if number of mappings is equal or less than
  * UID_GID_MAP_MAX_BASE_EXTENTS.
  */
 static struct uid_gid_extent *
 map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
 {
     unsigned idx;
     u32 first, last, id2;
 
     id2 = id + count - 1;
 
     /* Find the matching extent */
     for (idx = 0; idx < extents; idx++) {
         first = map->extent[idx].first;
         last = first + map->extent[idx].count - 1;
         if (id >= first && id <= last &&
             (id2 >= first && id2 <= last))
             return &map->extent[idx];
     }
     return NULL;
 }
 
 static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
 {
     struct uid_gid_extent *extent;
     unsigned extents = map->nr_extents;
     smp_rmb();
 
     if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
         extent = map_id_range_down_base(extents, map, id, count);
     else
         extent = map_id_range_down_max(extents, map, id, count);
 
     /* Map the id or note failure */
     if (extent)
         id = (id - extent->first) + extent->lower_first;
     else
         id = (u32) -1;
 
     return id;
 }
 
 static u32 map_id_down(struct uid_gid_map *map, u32 id)
 {
     return map_id_range_down(map, id, 1);
 }
 
 /**
  * map_id_up_base - Find idmap via binary search in static extent array.
  * Can only be called if number of mappings is equal or less than
  * UID_GID_MAP_MAX_BASE_EXTENTS.
  */
 static struct uid_gid_extent *
 map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id)
 {
     unsigned idx;
     u32 first, last;
 
     /* Find the matching extent */
     for (idx = 0; idx < extents; idx++) {
         first = map->extent[idx].lower_first;
         last = first + map->extent[idx].count - 1;
         if (id >= first && id <= last)
             return &map->extent[idx];
     }
     return NULL;
 }
 
 /**
  * map_id_up_max - Find idmap via binary search in ordered idmap array.
  * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
  */
 static struct uid_gid_extent *
 map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id)
 {
     struct idmap_key key;
 
     key.map_up = true;
     key.count = 1;
     key.id = id;
 
     return bsearch(&key, map->reverse, extents,
                sizeof(struct uid_gid_extent), cmp_map_id);
 }
 
 static u32 map_id_up(struct uid_gid_map *map, u32 id)
 {
     struct uid_gid_extent *extent;
     unsigned extents = map->nr_extents;
     smp_rmb();
 
     if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
         extent = map_id_up_base(extents, map, id);
     else
         extent = map_id_up_max(extents, map, id);
 
     /* Map the id or note failure */
     if (extent)
         id = (id - extent->lower_first) + extent->first;
     else
         id = (u32) -1;
 
     return id;
 }
 
 /**
  *  make_kuid - Map a user-namespace uid pair into a kuid.
  *  @ns:  User namespace that the uid is in
  *  @uid: User identifier
  *
  *  Maps a user-namespace uid pair into a kernel internal kuid,
  *  and returns that kuid.
  *
  *  When there is no mapping defined for the user-namespace uid
  *  pair INVALID_UID is returned.  Callers are expected to test
  *  for and handle INVALID_UID being returned.  INVALID_UID
  *  may be tested for using uid_valid().
  */
 kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
 {
     /* Map the uid to a global kernel uid */
     return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
 }
 EXPORT_SYMBOL(make_kuid);
 
 /**
  *  from_kuid - Create a uid from a kuid user-namespace pair.
  *  @targ: The user namespace we want a uid in.
  *  @kuid: The kernel internal uid to start with.
  *
  *  Map @kuid into the user-namespace specified by @targ and
  *  return the resulting uid.
  *
  *  There is always a mapping into the initial user_namespace.
  *
  *  If @kuid has no mapping in @targ (uid_t)-1 is returned.
  */
 uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
 {
     /* Map the uid from a global kernel uid */
     return map_id_up(&targ->uid_map, __kuid_val(kuid));
 }
 EXPORT_SYMBOL(from_kuid);
 
 /**
  *  from_kuid_munged - Create a uid from a kuid user-namespace pair.
  *  @targ: The user namespace we want a uid in.
  *  @kuid: The kernel internal uid to start with.
  *
  *  Map @kuid into the user-namespace specified by @targ and
  *  return the resulting uid.
  *
  *  There is always a mapping into the initial user_namespace.
  *
  *  Unlike from_kuid from_kuid_munged never fails and always
  *  returns a valid uid.  This makes from_kuid_munged appropriate
  *  for use in syscalls like stat and getuid where failing the
  *  system call and failing to provide a valid uid are not an
  *  options.
  *
  *  If @kuid has no mapping in @targ overflowuid is returned.
  */
 uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
 {
     uid_t uid;
     uid = from_kuid(targ, kuid);
 
     if (uid == (uid_t) -1)
         uid = overflowuid;
     return uid;
 }
 EXPORT_SYMBOL(from_kuid_munged);
 
 /**
  *  make_kgid - Map a user-namespace gid pair into a kgid.
  *  @ns:  User namespace that the gid is in
  *  @gid: group identifier
  *
  *  Maps a user-namespace gid pair into a kernel internal kgid,
  *  and returns that kgid.
  *
  *  When there is no mapping defined for the user-namespace gid
  *  pair INVALID_GID is returned.  Callers are expected to test
  *  for and handle INVALID_GID being returned.  INVALID_GID may be
  *  tested for using gid_valid().
  */
 kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
 {
     /* Map the gid to a global kernel gid */
     return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
 }
 EXPORT_SYMBOL(make_kgid);
 
 /**
  *  from_kgid - Create a gid from a kgid user-namespace pair.
  *  @targ: The user namespace we want a gid in.
  *  @kgid: The kernel internal gid to start with.
  *
  *  Map @kgid into the user-namespace specified by @targ and
  *  return the resulting gid.
  *
  *  There is always a mapping into the initial user_namespace.
  *
  *  If @kgid has no mapping in @targ (gid_t)-1 is returned.
  */
 gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
 {
     /* Map the gid from a global kernel gid */
     return map_id_up(&targ->gid_map, __kgid_val(kgid));
 }
 EXPORT_SYMBOL(from_kgid);
 
 /**
  *  from_kgid_munged - Create a gid from a kgid user-namespace pair.
  *  @targ: The user namespace we want a gid in.
  *  @kgid: The kernel internal gid to start with.
  *
  *  Map @kgid into the user-namespace specified by @targ and
  *  return the resulting gid.
  *
  *  There is always a mapping into the initial user_namespace.
  *
  *  Unlike from_kgid from_kgid_munged never fails and always
  *  returns a valid gid.  This makes from_kgid_munged appropriate
  *  for use in syscalls like stat and getgid where failing the
  *  system call and failing to provide a valid gid are not options.
  *
  *  If @kgid has no mapping in @targ overflowgid is returned.
  */
 gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
 {
     gid_t gid;
     gid = from_kgid(targ, kgid);
 
     if (gid == (gid_t) -1)
         gid = overflowgid;
     return gid;
 }
 EXPORT_SYMBOL(from_kgid_munged);
 
 /**
  *  make_kprojid - Map a user-namespace projid pair into a kprojid.
  *  @ns:  User namespace that the projid is in
  *  @projid: Project identifier
  *
  *  Maps a user-namespace uid pair into a kernel internal kuid,
  *  and returns that kuid.
  *
  *  When there is no mapping defined for the user-namespace projid
  *  pair INVALID_PROJID is returned.  Callers are expected to test
  *  for and handle INVALID_PROJID being returned.  INVALID_PROJID
  *  may be tested for using projid_valid().
  */
 kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
 {
     /* Map the uid to a global kernel uid */
     return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
 }
 EXPORT_SYMBOL(make_kprojid);
 
 /**
  *  from_kprojid - Create a projid from a kprojid user-namespace pair.
  *  @targ: The user namespace we want a projid in.
  *  @kprojid: The kernel internal project identifier to start with.
  *
  *  Map @kprojid into the user-namespace specified by @targ and
  *  return the resulting projid.
  *
  *  There is always a mapping into the initial user_namespace.
  *
  *  If @kprojid has no mapping in @targ (projid_t)-1 is returned.
  */
 projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
 {
     /* Map the uid from a global kernel uid */
     return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
 }
 EXPORT_SYMBOL(from_kprojid);
 
 /**
  *  from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
  *  @targ: The user namespace we want a projid in.
  *  @kprojid: The kernel internal projid to start with.
  *
  *  Map @kprojid into the user-namespace specified by @targ and
  *  return the resulting projid.
  *
  *  There is always a mapping into the initial user_namespace.
  *
  *  Unlike from_kprojid from_kprojid_munged never fails and always
  *  returns a valid projid.  This makes from_kprojid_munged
  *  appropriate for use in syscalls like stat and where
  *  failing the system call and failing to provide a valid projid are
  *  not an options.
  *
  *  If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
  */
 projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
 {
     projid_t projid;
     projid = from_kprojid(targ, kprojid);
 
     if (projid == (projid_t) -1)
         projid = OVERFLOW_PROJID;
     return projid;
 }
 EXPORT_SYMBOL(from_kprojid_munged);
 
 
 static int uid_m_show(struct seq_file *seq, void *v)
 {
     struct user_namespace *ns = seq->private;
     struct uid_gid_extent *extent = v;
     struct user_namespace *lower_ns;
     uid_t lower;
 
     lower_ns = seq_user_ns(seq);
     if ((lower_ns == ns) && lower_ns->parent)
         lower_ns = lower_ns->parent;
 
     lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
 
     seq_printf(seq, "%10u %10u %10u\n",
         extent->first,
         lower,
         extent->count);
 
     return 0;
 }
 
 static int gid_m_show(struct seq_file *seq, void *v)
 {
     struct user_namespace *ns = seq->private;
     struct uid_gid_extent *extent = v;
     struct user_namespace *lower_ns;
     gid_t lower;
 
     lower_ns = seq_user_ns(seq);
     if ((lower_ns == ns) && lower_ns->parent)
         lower_ns = lower_ns->parent;
 
     lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
 
     seq_printf(seq, "%10u %10u %10u\n",
         extent->first,
         lower,
         extent->count);
 
     return 0;
 }
 
 static int projid_m_show(struct seq_file *seq, void *v)
 {
     struct user_namespace *ns = seq->private;
     struct uid_gid_extent *extent = v;
     struct user_namespace *lower_ns;
     projid_t lower;
 
     lower_ns = seq_user_ns(seq);
     if ((lower_ns == ns) && lower_ns->parent)
         lower_ns = lower_ns->parent;
 
     lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
 
     seq_printf(seq, "%10u %10u %10u\n",
         extent->first,
         lower,
         extent->count);
 
     return 0;
 }
 
 static void *m_start(struct seq_file *seq, loff_t *ppos,
              struct uid_gid_map *map)
 {
     loff_t pos = *ppos;
     unsigned extents = map->nr_extents;
     smp_rmb();
 
     if (pos >= extents)
         return NULL;
 
     if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
         return &map->extent[pos];
 
     return &map->forward[pos];
 }
 
 static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
 {
     struct user_namespace *ns = seq->private;
 
     return m_start(seq, ppos, &ns->uid_map);
 }
 
 static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
 {
     struct user_namespace *ns = seq->private;
 
     return m_start(seq, ppos, &ns->gid_map);
 }
 
 static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
 {
     struct user_namespace *ns = seq->private;
 
     return m_start(seq, ppos, &ns->projid_map);
 }
 
 static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
 {
     (*pos)++;
     return seq->op->start(seq, pos);
 }
 
 static void m_stop(struct seq_file *seq, void *v)
 {
     return;
 }
 
 const struct seq_operations proc_uid_seq_operations = {
     .start = uid_m_start,
     .stop = m_stop,
     .next = m_next,
     .show = uid_m_show,
 };
 
 const struct seq_operations proc_gid_seq_operations = {
     .start = gid_m_start,
     .stop = m_stop,
     .next = m_next,
     .show = gid_m_show,
 };
 
 const struct seq_operations proc_projid_seq_operations = {
     .start = projid_m_start,
     .stop = m_stop,
     .next = m_next,
     .show = projid_m_show,
 };
 
 static bool mappings_overlap(struct uid_gid_map *new_map,
                  struct uid_gid_extent *extent)
 {
     u32 upper_first, lower_first, upper_last, lower_last;
     unsigned idx;
 
     upper_first = extent->first;
     lower_first = extent->lower_first;
     upper_last = upper_first + extent->count - 1;
     lower_last = lower_first + extent->count - 1;
 
     for (idx = 0; idx < new_map->nr_extents; idx++) {
         u32 prev_upper_first, prev_lower_first;
         u32 prev_upper_last, prev_lower_last;
         struct uid_gid_extent *prev;
 
         if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
             prev = &new_map->extent[idx];
         else
             prev = &new_map->forward[idx];
 
         prev_upper_first = prev->first;
         prev_lower_first = prev->lower_first;
         prev_upper_last = prev_upper_first + prev->count - 1;
         prev_lower_last = prev_lower_first + prev->count - 1;
 
         /* Does the upper range intersect a previous extent? */
         if ((prev_upper_first <= upper_last) &&
             (prev_upper_last >= upper_first))
             return true;
 
         /* Does the lower range intersect a previous extent? */
         if ((prev_lower_first <= lower_last) &&
             (prev_lower_last >= lower_first))
             return true;
     }
     return false;
 }
 
 /**
  * insert_extent - Safely insert a new idmap extent into struct uid_gid_map.
  * Takes care to allocate a 4K block of memory if the number of mappings exceeds
  * UID_GID_MAP_MAX_BASE_EXTENTS.
  */
 static int insert_extent(struct uid_gid_map *map, struct uid_gid_extent *extent)
 {
     struct uid_gid_extent *dest;
 
     if (map->nr_extents == UID_GID_MAP_MAX_BASE_EXTENTS) {
         struct uid_gid_extent *forward;
 
         /* Allocate memory for 340 mappings. */
         forward = kmalloc_array(UID_GID_MAP_MAX_EXTENTS,
                     sizeof(struct uid_gid_extent),
                     GFP_KERNEL);
         if (!forward)
             return -ENOMEM;
 
         /* Copy over memory. Only set up memory for the forward pointer.
          * Defer the memory setup for the reverse pointer.
          */
         memcpy(forward, map->extent,
                map->nr_extents * sizeof(map->extent[0]));
 
         map->forward = forward;
         map->reverse = NULL;
     }
 
     if (map->nr_extents < UID_GID_MAP_MAX_BASE_EXTENTS)
         dest = &map->extent[map->nr_extents];
     else
         dest = &map->forward[map->nr_extents];
 
     *dest = *extent;
     map->nr_extents++;
     return 0;
 }
 
 /* cmp function to sort() forward mappings */
 static int cmp_extents_forward(const void *a, const void *b)
 {
     const struct uid_gid_extent *e1 = a;
     const struct uid_gid_extent *e2 = b;
 
     if (e1->first < e2->first)
         return -1;
 
     if (e1->first > e2->first)
         return 1;
 
     return 0;
 }
 
 /* cmp function to sort() reverse mappings */
 static int cmp_extents_reverse(const void *a, const void *b)
 {
     const struct uid_gid_extent *e1 = a;
     const struct uid_gid_extent *e2 = b;
 
     if (e1->lower_first < e2->lower_first)
         return -1;
 
     if (e1->lower_first > e2->lower_first)
         return 1;
 
     return 0;
 }
 
 /**
  * sort_idmaps - Sorts an array of idmap entries.
  * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
  */
 static int sort_idmaps(struct uid_gid_map *map)
 {
     if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
         return 0;
 
     /* Sort forward array. */
     sort(map->forward, map->nr_extents, sizeof(struct uid_gid_extent),
          cmp_extents_forward, NULL);
 
     /* Only copy the memory from forward we actually need. */
     map->reverse = kmemdup(map->forward,
                    map->nr_extents * sizeof(struct uid_gid_extent),
                    GFP_KERNEL);
     if (!map->reverse)
         return -ENOMEM;
 
     /* Sort reverse array. */
     sort(map->reverse, map->nr_extents, sizeof(struct uid_gid_extent),
          cmp_extents_reverse, NULL);
 
     return 0;
 }
 
 /**
  * verify_root_map() - check the uid 0 mapping
  * @file: idmapping file
  * @map_ns: user namespace of the target process
  * @new_map: requested idmap
  *
  * If a process requests mapping parent uid 0 into the new ns, verify that the
  * process writing the map had the CAP_SETFCAP capability as the target process
  * will be able to write fscaps that are valid in ancestor user namespaces.
  *
  * Return: true if the mapping is allowed, false if not.
  */
 static bool verify_root_map(const struct file *file,
                 struct user_namespace *map_ns,
                 struct uid_gid_map *new_map)
 {
     int idx;
     const struct user_namespace *file_ns = file->f_cred->user_ns;
     struct uid_gid_extent *extent0 = NULL;
 
     for (idx = 0; idx < new_map->nr_extents; idx++) {
         if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
             extent0 = &new_map->extent[idx];
         else
             extent0 = &new_map->forward[idx];
         if (extent0->lower_first == 0)
             break;
 
         extent0 = NULL;
     }
 
     if (!extent0)
         return true;
 
     if (map_ns == file_ns) {
         /* The process unshared its ns and is writing to its own
          * /proc/self/uid_map.  User already has full capabilites in
          * the new namespace.  Verify that the parent had CAP_SETFCAP
          * when it unshared.
          * */
         if (!file_ns->parent_could_setfcap)
             return false;
     } else {
         /* Process p1 is writing to uid_map of p2, who is in a child
          * user namespace to p1's.  Verify that the opener of the map
          * file has CAP_SETFCAP against the parent of the new map
          * namespace */
         if (!file_ns_capable(file, map_ns->parent, CAP_SETFCAP))
             return false;
     }
 
     return true;
 }
 
 static ssize_t map_write(struct file *file, const char __user *buf,
              size_t count, loff_t *ppos,
              int cap_setid,
              struct uid_gid_map *map,
              struct uid_gid_map *parent_map)
 {
     struct seq_file *seq = file->private_data;
     struct user_namespace *map_ns = seq->private;
     struct uid_gid_map new_map;
     unsigned idx;
     struct uid_gid_extent extent;
     char *kbuf = NULL, *pos, *next_line;
     ssize_t ret;
 
     /* Only allow < page size writes at the beginning of the file */
     if ((*ppos != 0) || (count >= PAGE_SIZE))
         return -EINVAL;
 
     /* Slurp in the user data */
     kbuf = memdup_user_nul(buf, count);
     if (IS_ERR(kbuf))
         return PTR_ERR(kbuf);
 
     /*
      * The userns_state_mutex serializes all writes to any given map.
      *
      * Any map is only ever written once.
      *
      * An id map fits within 1 cache line on most architectures.
      *
      * On read nothing needs to be done unless you are on an
      * architecture with a crazy cache coherency model like alpha.
      *
      * There is a one time data dependency between reading the
      * count of the extents and the values of the extents.  The
      * desired behavior is to see the values of the extents that
      * were written before the count of the extents.
      *
      * To achieve this smp_wmb() is used on guarantee the write
      * order and smp_rmb() is guaranteed that we don't have crazy
      * architectures returning stale data.
      */
     mutex_lock(&userns_state_mutex);
 
     memset(&new_map, 0, sizeof(struct uid_gid_map));
 
     ret = -EPERM;
     /* Only allow one successful write to the map */
     if (map->nr_extents != 0)
         goto out;
 
     /*
      * Adjusting namespace settings requires capabilities on the target.
      */
     if (cap_valid(cap_setid) && !file_ns_capable(file, map_ns, CAP_SYS_ADMIN))
         goto out;
 
     /* Parse the user data */
     ret = -EINVAL;
     pos = kbuf;
     for (; pos; pos = next_line) {
 
         /* Find the end of line and ensure I don't look past it */
         next_line = strchr(pos, '\n');
         if (next_line) {
             *next_line = '\0';
             next_line++;
             if (*next_line == '\0')
                 next_line = NULL;
         }
 
         pos = skip_spaces(pos);
         extent.first = simple_strtoul(pos, &pos, 10);
         if (!isspace(*pos))
             goto out;
 
         pos = skip_spaces(pos);
         extent.lower_first = simple_strtoul(pos, &pos, 10);
         if (!isspace(*pos))
             goto out;
 
         pos = skip_spaces(pos);
         extent.count = simple_strtoul(pos, &pos, 10);
         if (*pos && !isspace(*pos))
             goto out;
 
         /* Verify there is not trailing junk on the line */
         pos = skip_spaces(pos);
         if (*pos != '\0')
             goto out;
 
         /* Verify we have been given valid starting values */
         if ((extent.first == (u32) -1) ||
             (extent.lower_first == (u32) -1))
             goto out;
 
         /* Verify count is not zero and does not cause the
          * extent to wrap
          */
         if ((extent.first + extent.count) <= extent.first)
             goto out;
         if ((extent.lower_first + extent.count) <=
              extent.lower_first)
             goto out;
 
         /* Do the ranges in extent overlap any previous extents? */
         if (mappings_overlap(&new_map, &extent))
             goto out;
 
         if ((new_map.nr_extents + 1) == UID_GID_MAP_MAX_EXTENTS &&
             (next_line != NULL))
             goto out;
 
         ret = insert_extent(&new_map, &extent);
         if (ret < 0)
             goto out;
         ret = -EINVAL;
     }
     /* Be very certain the new map actually exists */
     if (new_map.nr_extents == 0)
         goto out;
 
     ret = -EPERM;
     /* Validate the user is allowed to use user id's mapped to. */
     if (!new_idmap_permitted(file, map_ns, cap_setid, &new_map))
         goto out;
 
     ret = -EPERM;
     /* Map the lower ids from the parent user namespace to the
      * kernel global id space.
      */
     for (idx = 0; idx < new_map.nr_extents; idx++) {
         struct uid_gid_extent *e;
         u32 lower_first;
 
         if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
             e = &new_map.extent[idx];
         else
             e = &new_map.forward[idx];
 
         lower_first = map_id_range_down(parent_map,
                         e->lower_first,
                         e->count);
 
         /* Fail if we can not map the specified extent to
          * the kernel global id space.
          */
         if (lower_first == (u32) -1)
             goto out;
 
         e->lower_first = lower_first;
     }
 
     /*
      * If we want to use binary search for lookup, this clones the extent
      * array and sorts both copies.
      */
     ret = sort_idmaps(&new_map);
     if (ret < 0)
         goto out;
 
     /* Install the map */
     if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) {
         memcpy(map->extent, new_map.extent,
                new_map.nr_extents * sizeof(new_map.extent[0]));
     } else {
         map->forward = new_map.forward;
         map->reverse = new_map.reverse;
     }
     smp_wmb();
     map->nr_extents = new_map.nr_extents;
 
     *ppos = count;
     ret = count;
 out:
     if (ret < 0 && new_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
         kfree(new_map.forward);
         kfree(new_map.reverse);
         map->forward = NULL;
         map->reverse = NULL;
         map->nr_extents = 0;
     }
 
     mutex_unlock(&userns_state_mutex);
     kfree(kbuf);
     return ret;
 }
 
 ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
                size_t size, loff_t *ppos)
 {
     struct seq_file *seq = file->private_data;
     struct user_namespace *ns = seq->private;
     struct user_namespace *seq_ns = seq_user_ns(seq);
 
     if (!ns->parent)
         return -EPERM;
 
     if ((seq_ns != ns) && (seq_ns != ns->parent))
         return -EPERM;
 
     return map_write(file, buf, size, ppos, CAP_SETUID,
              &ns->uid_map, &ns->parent->uid_map);
 }
 
 ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
                size_t size, loff_t *ppos)
 {
     struct seq_file *seq = file->private_data;
     struct user_namespace *ns = seq->private;
     struct user_namespace *seq_ns = seq_user_ns(seq);
 
     if (!ns->parent)
         return -EPERM;
 
     if ((seq_ns != ns) && (seq_ns != ns->parent))
         return -EPERM;
 
     return map_write(file, buf, size, ppos, CAP_SETGID,
              &ns->gid_map, &ns->parent->gid_map);
 }
 
 ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
                   size_t size, loff_t *ppos)
 {
     struct seq_file *seq = file->private_data;
     struct user_namespace *ns = seq->private;
     struct user_namespace *seq_ns = seq_user_ns(seq);
 
     if (!ns->parent)
         return -EPERM;
 
     if ((seq_ns != ns) && (seq_ns != ns->parent))
         return -EPERM;
 
     /* Anyone can set any valid project id no capability needed */
     return map_write(file, buf, size, ppos, -1,
              &ns->projid_map, &ns->parent->projid_map);
 }
 
 static bool new_idmap_permitted(const struct file *file,
                 struct user_namespace *ns, int cap_setid,
                 struct uid_gid_map *new_map)
 {
     const struct cred *cred = file->f_cred;
 
     if (cap_setid == CAP_SETUID && !verify_root_map(file, ns, new_map))
         return false;
 
     /* Don't allow mappings that would allow anything that wouldn't
      * be allowed without the establishment of unprivileged mappings.
      */
     if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
         uid_eq(ns->owner, cred->euid)) {
         u32 id = new_map->extent[0].lower_first;
         if (cap_setid == CAP_SETUID) {
             kuid_t uid = make_kuid(ns->parent, id);
             if (uid_eq(uid, cred->euid))
                 return true;
         } else if (cap_setid == CAP_SETGID) {
             kgid_t gid = make_kgid(ns->parent, id);
             if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
                 gid_eq(gid, cred->egid))
                 return true;
         }
     }
 
     /* Allow anyone to set a mapping that doesn't require privilege */
     if (!cap_valid(cap_setid))
         return true;
 
     /* Allow the specified ids if we have the appropriate capability
      * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
      * And the opener of the id file also has the appropriate capability.
      */
     if (ns_capable(ns->parent, cap_setid) &&
         file_ns_capable(file, ns->parent, cap_setid))
         return true;
 
     return false;
 }
 
 int proc_setgroups_show(struct seq_file *seq, void *v)
 {
     struct user_namespace *ns = seq->private;
     unsigned long userns_flags = READ_ONCE(ns->flags);
 
     seq_printf(seq, "%s\n",
            (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
            "allow" : "deny");
     return 0;
 }
 
 ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
                  size_t count, loff_t *ppos)
 {
     struct seq_file *seq = file->private_data;
     struct user_namespace *ns = seq->private;
     char kbuf[8], *pos;
     bool setgroups_allowed;
     ssize_t ret;
 
     /* Only allow a very narrow range of strings to be written */
     ret = -EINVAL;
     if ((*ppos != 0) || (count >= sizeof(kbuf)))
         goto out;
 
     /* What was written? */
     ret = -EFAULT;
     if (copy_from_user(kbuf, buf, count))
         goto out;
     kbuf[count] = '\0';
     pos = kbuf;
 
     /* What is being requested? */
     ret = -EINVAL;
     if (strncmp(pos, "allow", 5) == 0) {
         pos += 5;
         setgroups_allowed = true;
     }
     else if (strncmp(pos, "deny", 4) == 0) {
         pos += 4;
         setgroups_allowed = false;
     }
     else
         goto out;
 
     /* Verify there is not trailing junk on the line */
     pos = skip_spaces(pos);
     if (*pos != '\0')
         goto out;
 
     ret = -EPERM;
     mutex_lock(&userns_state_mutex);
     if (setgroups_allowed) {
         /* Enabling setgroups after setgroups has been disabled
          * is not allowed.
          */
         if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
             goto out_unlock;
     } else {
         /* Permanently disabling setgroups after setgroups has
          * been enabled by writing the gid_map is not allowed.
          */
         if (ns->gid_map.nr_extents != 0)
             goto out_unlock;
         ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
     }
     mutex_unlock(&userns_state_mutex);
 
     /* Report a successful write */
     *ppos = count;
     ret = count;
 out:
     return ret;
 out_unlock:
     mutex_unlock(&userns_state_mutex);
     goto out;
 }
 
 bool userns_may_setgroups(const struct user_namespace *ns)
 {
     bool allowed;
 
     mutex_lock(&userns_state_mutex);
     /* It is not safe to use setgroups until a gid mapping in
      * the user namespace has been established.
      */
     allowed = ns->gid_map.nr_extents != 0;
     /* Is setgroups allowed? */
     allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
     mutex_unlock(&userns_state_mutex);
 
     return allowed;
 }
 
 /*
  * Returns true if @child is the same namespace or a descendant of
  * @ancestor.
  */
 bool in_userns(const struct user_namespace *ancestor,
            const struct user_namespace *child)
 {
     const struct user_namespace *ns;
     for (ns = child; ns->level > ancestor->level; ns = ns->parent)
         ;
     return (ns == ancestor);
 }
 
 bool current_in_userns(const struct user_namespace *target_ns)
 {
     return in_userns(target_ns, current_user_ns());
 }
 EXPORT_SYMBOL(current_in_userns);
 
 static inline struct user_namespace *to_user_ns(struct ns_common *ns)
 {
     return container_of(ns, struct user_namespace, ns);
 }
 
 static struct ns_common *userns_get(struct task_struct *task)
 {
     struct user_namespace *user_ns;
 
     rcu_read_lock();
     user_ns = get_user_ns(__task_cred(task)->user_ns);
     rcu_read_unlock();
 
     return user_ns ? &user_ns->ns : NULL;
 }
 
 static void userns_put(struct ns_common *ns)
 {
     put_user_ns(to_user_ns(ns));
 }
 
 static int userns_install(struct nsset *nsset, struct ns_common *ns)
 {
     struct user_namespace *user_ns = to_user_ns(ns);
     struct cred *cred;
 
     /* Don't allow gaining capabilities by reentering
      * the same user namespace.
      */
     if (user_ns == current_user_ns())
         return -EINVAL;
 
     /* Tasks that share a thread group must share a user namespace */
     if (!thread_group_empty(current))
         return -EINVAL;
 
     if (current->fs->users != 1)
         return -EINVAL;
 
     if (!ns_capable(user_ns, CAP_SYS_ADMIN))
         return -EPERM;
 
     cred = nsset_cred(nsset);
     if (!cred)
         return -EINVAL;
 
     put_user_ns(cred->user_ns);
     set_cred_user_ns(cred, get_user_ns(user_ns));
 
     if (set_cred_ucounts(cred) < 0)
         return -EINVAL;
 
     return 0;
 }
 
 struct ns_common *ns_get_owner(struct ns_common *ns)
 {
     struct user_namespace *my_user_ns = current_user_ns();
     struct user_namespace *owner, *p;
 
     /* See if the owner is in the current user namespace */
     owner = p = ns->ops->owner(ns);
     for (;;) {
         if (!p)
             return ERR_PTR(-EPERM);
         if (p == my_user_ns)
             break;
         p = p->parent;
     }
 
     return &get_user_ns(owner)->ns;
 }
 
 static struct user_namespace *userns_owner(struct ns_common *ns)
 {
     return to_user_ns(ns)->parent;
 }
 
 const struct proc_ns_operations userns_operations = {
     .name       = "user",
     .type       = CLONE_NEWUSER,
     .get        = userns_get,
     .put        = userns_put,
     .install    = userns_install,
     .owner      = userns_owner,
     .get_parent = ns_get_owner,
 };
 
 static __init int user_namespaces_init(void)
 {
     user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC | SLAB_ACCOUNT);
     return 0;
 }
 subsys_initcall(user_namespaces_init);

This page was automatically generated by the 2.1.0 LXR engine. The LXR team