#include <linux/user_namespace.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>
static struct kmem_cache *user_ns_cachep __read_mostly;
+static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
+ struct uid_gid_map *map);
+
/*
* 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
*/
int create_user_ns(struct cred *new)
{
- struct user_namespace *ns;
- struct user_struct *root_user;
- int n;
+ struct user_namespace *ns, *parent_ns = new->user_ns;
+ kuid_t owner = new->euid;
+ kgid_t group = new->egid;
+
+ /* 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.
+ */
+ if (!kuid_has_mapping(parent_ns, owner) ||
+ !kgid_has_mapping(parent_ns, group))
+ return -EPERM;
- ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL);
+ ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
if (!ns)
return -ENOMEM;
kref_init(&ns->kref);
+ ns->parent = parent_ns;
+ ns->owner = owner;
+ ns->group = group;
- for (n = 0; n < UIDHASH_SZ; ++n)
- INIT_HLIST_HEAD(ns->uidhash_table + n);
-
- /* Alloc new root user. */
- root_user = alloc_uid(ns, 0);
- if (!root_user) {
- kmem_cache_free(user_ns_cachep, ns);
- return -ENOMEM;
- }
-
- /* set the new root user in the credentials under preparation */
- ns->creator = new->user;
- new->user = root_user;
- new->uid = new->euid = new->suid = new->fsuid = 0;
- new->gid = new->egid = new->sgid = new->fsgid = 0;
- put_group_info(new->group_info);
- new->group_info = get_group_info(&init_groups);
+ /* Start with the same capabilities as init but useless for doing
+ * anything as the capabilities are bound to the new user namespace.
+ */
+ new->securebits = SECUREBITS_DEFAULT;
+ new->cap_inheritable = CAP_EMPTY_SET;
+ new->cap_permitted = CAP_FULL_SET;
+ new->cap_effective = CAP_FULL_SET;
+ new->cap_bset = CAP_FULL_SET;
#ifdef CONFIG_KEYS
key_put(new->request_key_auth);
new->request_key_auth = NULL;
#endif
/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
- /* root_user holds a reference to ns, our reference can be dropped */
- put_user_ns(ns);
+ /* Leave the new->user_ns reference with the new user namespace. */
+ /* Leave the reference to our user_ns with the new cred. */
+ new->user_ns = ns;
return 0;
}
-/*
- * Deferred destructor for a user namespace. This is required because
- * free_user_ns() may be called with uidhash_lock held, but we need to call
- * back to free_uid() which will want to take the lock again.
- */
-static void free_user_ns_work(struct work_struct *work)
+void free_user_ns(struct kref *kref)
{
- struct user_namespace *ns =
- container_of(work, struct user_namespace, destroyer);
- free_uid(ns->creator);
+ struct user_namespace *parent, *ns =
+ container_of(kref, struct user_namespace, kref);
+
+ parent = ns->parent;
kmem_cache_free(user_ns_cachep, ns);
+ put_user_ns(parent);
}
+EXPORT_SYMBOL(free_user_ns);
-void free_user_ns(struct kref *kref)
+static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
{
- struct user_namespace *ns =
- container_of(kref, struct user_namespace, kref);
+ unsigned idx, extents;
+ u32 first, last, id2;
+
+ id2 = id + count - 1;
+
+ /* Find the matching extent */
+ extents = map->nr_extents;
+ smp_read_barrier_depends();
+ 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))
+ break;
+ }
+ /* Map the id or note failure */
+ if (idx < extents)
+ id = (id - first) + map->extent[idx].lower_first;
+ else
+ id = (u32) -1;
- INIT_WORK(&ns->destroyer, free_user_ns_work);
- schedule_work(&ns->destroyer);
+ return id;
}
-EXPORT_SYMBOL(free_user_ns);
-uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid)
+static u32 map_id_down(struct uid_gid_map *map, u32 id)
{
- struct user_namespace *tmp;
+ unsigned idx, extents;
+ u32 first, last;
- if (likely(to == cred->user->user_ns))
- return uid;
+ /* Find the matching extent */
+ extents = map->nr_extents;
+ smp_read_barrier_depends();
+ for (idx = 0; idx < extents; idx++) {
+ first = map->extent[idx].first;
+ last = first + map->extent[idx].count - 1;
+ if (id >= first && id <= last)
+ break;
+ }
+ /* Map the id or note failure */
+ if (idx < extents)
+ id = (id - first) + map->extent[idx].lower_first;
+ else
+ id = (u32) -1;
+ return id;
+}
- /* Is cred->user the creator of the target user_ns
- * or the creator of one of it's parents?
- */
- for ( tmp = to; tmp != &init_user_ns;
- tmp = tmp->creator->user_ns ) {
- if (cred->user == tmp->creator) {
- return (uid_t)0;
- }
+static u32 map_id_up(struct uid_gid_map *map, u32 id)
+{
+ unsigned idx, extents;
+ u32 first, last;
+
+ /* Find the matching extent */
+ extents = map->nr_extents;
+ smp_read_barrier_depends();
+ for (idx = 0; idx < extents; idx++) {
+ first = map->extent[idx].lower_first;
+ last = first + map->extent[idx].count - 1;
+ if (id >= first && id <= last)
+ break;
}
+ /* Map the id or note failure */
+ if (idx < extents)
+ id = (id - first) + map->extent[idx].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 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);
- /* No useful relationship so no mapping */
- return overflowuid;
+/**
+ * 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);
-gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid)
+/**
+ * make_kgid - Map a user-namespace gid pair into a kgid.
+ * @ns: User namespace that the gid is in
+ * @uid: 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)
{
- struct user_namespace *tmp;
+ /* Map the gid to a global kernel gid */
+ return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
+}
+EXPORT_SYMBOL(make_kgid);
- if (likely(to == cred->user->user_ns))
- return gid;
+/**
+ * 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);
- /* Is cred->user the creator of the target user_ns
- * or the creator of one of it's parents?
+ if (gid == (gid_t) -1)
+ gid = overflowgid;
+ return gid;
+}
+EXPORT_SYMBOL(from_kgid_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 = current_user_ns();
+ 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 = current_user_ns();
+ 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 void *m_start(struct seq_file *seq, loff_t *ppos, struct uid_gid_map *map)
+{
+ struct uid_gid_extent *extent = NULL;
+ loff_t pos = *ppos;
+
+ if (pos < map->nr_extents)
+ extent = &map->extent[pos];
+
+ return extent;
+}
+
+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 *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;
+}
+
+struct seq_operations proc_uid_seq_operations = {
+ .start = uid_m_start,
+ .stop = m_stop,
+ .next = m_next,
+ .show = uid_m_show,
+};
+
+struct seq_operations proc_gid_seq_operations = {
+ .start = gid_m_start,
+ .stop = m_stop,
+ .next = m_next,
+ .show = gid_m_show,
+};
+
+static DEFINE_MUTEX(id_map_mutex);
+
+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 *ns = seq->private;
+ struct uid_gid_map new_map;
+ unsigned idx;
+ struct uid_gid_extent *extent, *last = NULL;
+ unsigned long page = 0;
+ char *kbuf, *pos, *next_line;
+ ssize_t ret = -EINVAL;
+
+ /*
+ * The id_map_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_read_barrier_depends() is guaranteed that we
+ * don't have crazy architectures returning stale data.
+ *
*/
- for ( tmp = to; tmp != &init_user_ns;
- tmp = tmp->creator->user_ns ) {
- if (cred->user == tmp->creator) {
- return (gid_t)0;
+ mutex_lock(&id_map_mutex);
+
+ ret = -EPERM;
+ /* Only allow one successful write to the map */
+ if (map->nr_extents != 0)
+ goto out;
+
+ /* Require the appropriate privilege CAP_SETUID or CAP_SETGID
+ * over the user namespace in order to set the id mapping.
+ */
+ if (!ns_capable(ns, cap_setid))
+ goto out;
+
+ /* Get a buffer */
+ ret = -ENOMEM;
+ page = __get_free_page(GFP_TEMPORARY);
+ kbuf = (char *) page;
+ if (!page)
+ goto out;
+
+ /* Only allow <= page size writes at the beginning of the file */
+ ret = -EINVAL;
+ if ((*ppos != 0) || (count >= PAGE_SIZE))
+ goto out;
+
+ /* Slurp in the user data */
+ ret = -EFAULT;
+ if (copy_from_user(kbuf, buf, count))
+ goto out;
+ kbuf[count] = '\0';
+
+ /* Parse the user data */
+ ret = -EINVAL;
+ pos = kbuf;
+ new_map.nr_extents = 0;
+ for (;pos; pos = next_line) {
+ extent = &new_map.extent[new_map.nr_extents];
+
+ /* 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;
+
+ /* For now only accept extents that are strictly in order */
+ if (last &&
+ (((last->first + last->count) > extent->first) ||
+ ((last->lower_first + last->count) > extent->lower_first)))
+ goto out;
+
+ new_map.nr_extents++;
+ last = extent;
+
+ /* Fail if the file contains too many extents */
+ if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
+ (next_line != NULL))
+ goto out;
+ }
+ /* Be very certaint 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(ns, cap_setid, &new_map))
+ goto out;
+
+ /* Map the lower ids from the parent user namespace to the
+ * kernel global id space.
+ */
+ for (idx = 0; idx < new_map.nr_extents; idx++) {
+ u32 lower_first;
+ extent = &new_map.extent[idx];
+
+ lower_first = map_id_range_down(parent_map,
+ extent->lower_first,
+ extent->count);
+
+ /* Fail if we can not map the specified extent to
+ * the kernel global id space.
+ */
+ if (lower_first == (u32) -1)
+ goto out;
+
+ extent->lower_first = lower_first;
}
- /* No useful relationship so no mapping */
- return overflowgid;
+ /* Install the map */
+ memcpy(map->extent, new_map.extent,
+ new_map.nr_extents*sizeof(new_map.extent[0]));
+ smp_wmb();
+ map->nr_extents = new_map.nr_extents;
+
+ *ppos = count;
+ ret = count;
+out:
+ mutex_unlock(&id_map_mutex);
+ if (page)
+ free_page(page);
+ 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;
+
+ if (!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;
+
+ if (!ns->parent)
+ return -EPERM;
+
+ return map_write(file, buf, size, ppos, CAP_SETGID,
+ &ns->gid_map, &ns->parent->gid_map);
+}
+
+static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
+ struct uid_gid_map *new_map)
+{
+ /* Allow the specified ids if we have the appropriate capability
+ * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
+ */
+ if (ns_capable(ns->parent, cap_setid))
+ return true;
+
+ return false;
}
static __init int user_namespaces_init(void)
git.openpandora.org / pandora-kernel.git / blobdiff