078de5f706
cred.h and a few trivial users of struct cred are changed. The rest of the users of struct cred are left for other patches as there are too many changes to make in one go and leave the change reviewable. If the user namespace is disabled and CONFIG_UIDGID_STRICT_TYPE_CHECKS are disabled the code will contiue to compile and behave correctly. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
605 lines
15 KiB
C
605 lines
15 KiB
C
/*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*/
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#include <linux/export.h>
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#include <linux/nsproxy.h>
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#include <linux/slab.h>
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#include <linux/user_namespace.h>
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#include <linux/highuid.h>
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#include <linux/cred.h>
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#include <linux/securebits.h>
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#include <linux/keyctl.h>
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#include <linux/key-type.h>
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#include <keys/user-type.h>
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#include <linux/seq_file.h>
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#include <linux/fs.h>
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#include <linux/uaccess.h>
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#include <linux/ctype.h>
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static struct kmem_cache *user_ns_cachep __read_mostly;
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static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
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struct uid_gid_map *map);
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/*
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* Create a new user namespace, deriving the creator from the user in the
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* passed credentials, and replacing that user with the new root user for the
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* new namespace.
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*
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* This is called by copy_creds(), which will finish setting the target task's
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* credentials.
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*/
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int create_user_ns(struct cred *new)
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{
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struct user_namespace *ns, *parent_ns = new->user_ns;
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kuid_t owner = new->euid;
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kgid_t group = new->egid;
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/* The creator needs a mapping in the parent user namespace
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* or else we won't be able to reasonably tell userspace who
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* created a user_namespace.
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*/
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if (!kuid_has_mapping(parent_ns, owner) ||
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!kgid_has_mapping(parent_ns, group))
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return -EPERM;
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ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
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if (!ns)
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return -ENOMEM;
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kref_init(&ns->kref);
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ns->parent = parent_ns;
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ns->owner = owner;
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ns->group = group;
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/* Start with the same capabilities as init but useless for doing
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* anything as the capabilities are bound to the new user namespace.
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*/
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new->securebits = SECUREBITS_DEFAULT;
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new->cap_inheritable = CAP_EMPTY_SET;
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new->cap_permitted = CAP_FULL_SET;
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new->cap_effective = CAP_FULL_SET;
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new->cap_bset = CAP_FULL_SET;
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#ifdef CONFIG_KEYS
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key_put(new->request_key_auth);
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new->request_key_auth = NULL;
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#endif
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/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
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/* Leave the new->user_ns reference with the new user namespace. */
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/* Leave the reference to our user_ns with the new cred. */
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new->user_ns = ns;
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return 0;
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}
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void free_user_ns(struct kref *kref)
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{
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struct user_namespace *parent, *ns =
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container_of(kref, struct user_namespace, kref);
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parent = ns->parent;
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kmem_cache_free(user_ns_cachep, ns);
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put_user_ns(parent);
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}
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EXPORT_SYMBOL(free_user_ns);
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static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
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{
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unsigned idx, extents;
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u32 first, last, id2;
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id2 = id + count - 1;
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/* Find the matching extent */
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extents = map->nr_extents;
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smp_read_barrier_depends();
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for (idx = 0; idx < extents; idx++) {
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first = map->extent[idx].first;
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last = first + map->extent[idx].count - 1;
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if (id >= first && id <= last &&
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(id2 >= first && id2 <= last))
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break;
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}
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/* Map the id or note failure */
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if (idx < extents)
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id = (id - first) + map->extent[idx].lower_first;
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else
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id = (u32) -1;
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return id;
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}
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static u32 map_id_down(struct uid_gid_map *map, u32 id)
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{
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unsigned idx, extents;
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u32 first, last;
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/* Find the matching extent */
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extents = map->nr_extents;
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smp_read_barrier_depends();
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for (idx = 0; idx < extents; idx++) {
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first = map->extent[idx].first;
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last = first + map->extent[idx].count - 1;
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if (id >= first && id <= last)
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break;
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}
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/* Map the id or note failure */
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if (idx < extents)
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id = (id - first) + map->extent[idx].lower_first;
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else
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id = (u32) -1;
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return id;
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}
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static u32 map_id_up(struct uid_gid_map *map, u32 id)
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{
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unsigned idx, extents;
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u32 first, last;
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/* Find the matching extent */
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extents = map->nr_extents;
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smp_read_barrier_depends();
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for (idx = 0; idx < extents; idx++) {
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first = map->extent[idx].lower_first;
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last = first + map->extent[idx].count - 1;
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if (id >= first && id <= last)
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break;
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}
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/* Map the id or note failure */
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if (idx < extents)
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id = (id - first) + map->extent[idx].first;
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else
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id = (u32) -1;
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return id;
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}
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/**
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* make_kuid - Map a user-namespace uid pair into a kuid.
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* @ns: User namespace that the uid is in
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* @uid: User identifier
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*
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* Maps a user-namespace uid pair into a kernel internal kuid,
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* and returns that kuid.
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*
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* When there is no mapping defined for the user-namespace uid
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* pair INVALID_UID is returned. Callers are expected to test
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* for and handle handle INVALID_UID being returned. INVALID_UID
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* may be tested for using uid_valid().
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*/
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kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
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{
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/* Map the uid to a global kernel uid */
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return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
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}
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EXPORT_SYMBOL(make_kuid);
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/**
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* from_kuid - Create a uid from a kuid user-namespace pair.
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* @targ: The user namespace we want a uid in.
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* @kuid: The kernel internal uid to start with.
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*
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* Map @kuid into the user-namespace specified by @targ and
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* return the resulting uid.
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*
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* There is always a mapping into the initial user_namespace.
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*
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* If @kuid has no mapping in @targ (uid_t)-1 is returned.
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*/
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uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
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{
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/* Map the uid from a global kernel uid */
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return map_id_up(&targ->uid_map, __kuid_val(kuid));
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}
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EXPORT_SYMBOL(from_kuid);
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/**
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* from_kuid_munged - Create a uid from a kuid user-namespace pair.
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* @targ: The user namespace we want a uid in.
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* @kuid: The kernel internal uid to start with.
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*
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* Map @kuid into the user-namespace specified by @targ and
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* return the resulting uid.
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*
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* There is always a mapping into the initial user_namespace.
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*
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* Unlike from_kuid from_kuid_munged never fails and always
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* returns a valid uid. This makes from_kuid_munged appropriate
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* for use in syscalls like stat and getuid where failing the
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* system call and failing to provide a valid uid are not an
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* options.
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*
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* If @kuid has no mapping in @targ overflowuid is returned.
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*/
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uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
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{
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uid_t uid;
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uid = from_kuid(targ, kuid);
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if (uid == (uid_t) -1)
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uid = overflowuid;
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return uid;
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}
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EXPORT_SYMBOL(from_kuid_munged);
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/**
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* make_kgid - Map a user-namespace gid pair into a kgid.
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* @ns: User namespace that the gid is in
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* @uid: group identifier
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*
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* Maps a user-namespace gid pair into a kernel internal kgid,
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* and returns that kgid.
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*
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* When there is no mapping defined for the user-namespace gid
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* pair INVALID_GID is returned. Callers are expected to test
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* for and handle INVALID_GID being returned. INVALID_GID may be
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* tested for using gid_valid().
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*/
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kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
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{
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/* Map the gid to a global kernel gid */
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return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
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}
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EXPORT_SYMBOL(make_kgid);
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/**
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* from_kgid - Create a gid from a kgid user-namespace pair.
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* @targ: The user namespace we want a gid in.
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* @kgid: The kernel internal gid to start with.
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*
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* Map @kgid into the user-namespace specified by @targ and
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* return the resulting gid.
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*
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* There is always a mapping into the initial user_namespace.
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*
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* If @kgid has no mapping in @targ (gid_t)-1 is returned.
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*/
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gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
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{
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/* Map the gid from a global kernel gid */
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return map_id_up(&targ->gid_map, __kgid_val(kgid));
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}
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EXPORT_SYMBOL(from_kgid);
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/**
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* from_kgid_munged - Create a gid from a kgid user-namespace pair.
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* @targ: The user namespace we want a gid in.
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* @kgid: The kernel internal gid to start with.
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*
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* Map @kgid into the user-namespace specified by @targ and
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* return the resulting gid.
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*
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* There is always a mapping into the initial user_namespace.
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*
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* Unlike from_kgid from_kgid_munged never fails and always
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* returns a valid gid. This makes from_kgid_munged appropriate
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* for use in syscalls like stat and getgid where failing the
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* system call and failing to provide a valid gid are not options.
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*
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* If @kgid has no mapping in @targ overflowgid is returned.
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*/
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gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
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{
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gid_t gid;
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gid = from_kgid(targ, kgid);
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if (gid == (gid_t) -1)
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gid = overflowgid;
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return gid;
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}
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EXPORT_SYMBOL(from_kgid_munged);
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static int uid_m_show(struct seq_file *seq, void *v)
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{
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struct user_namespace *ns = seq->private;
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struct uid_gid_extent *extent = v;
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struct user_namespace *lower_ns;
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uid_t lower;
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lower_ns = current_user_ns();
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if ((lower_ns == ns) && lower_ns->parent)
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lower_ns = lower_ns->parent;
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lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
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seq_printf(seq, "%10u %10u %10u\n",
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extent->first,
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lower,
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extent->count);
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return 0;
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}
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static int gid_m_show(struct seq_file *seq, void *v)
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{
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struct user_namespace *ns = seq->private;
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struct uid_gid_extent *extent = v;
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struct user_namespace *lower_ns;
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gid_t lower;
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lower_ns = current_user_ns();
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if ((lower_ns == ns) && lower_ns->parent)
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lower_ns = lower_ns->parent;
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lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
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seq_printf(seq, "%10u %10u %10u\n",
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extent->first,
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lower,
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extent->count);
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return 0;
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}
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static void *m_start(struct seq_file *seq, loff_t *ppos, struct uid_gid_map *map)
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{
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struct uid_gid_extent *extent = NULL;
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loff_t pos = *ppos;
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if (pos < map->nr_extents)
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extent = &map->extent[pos];
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return extent;
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}
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static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
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{
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struct user_namespace *ns = seq->private;
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return m_start(seq, ppos, &ns->uid_map);
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}
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static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
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{
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struct user_namespace *ns = seq->private;
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return m_start(seq, ppos, &ns->gid_map);
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}
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static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
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{
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(*pos)++;
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return seq->op->start(seq, pos);
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}
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static void m_stop(struct seq_file *seq, void *v)
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{
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return;
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}
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struct seq_operations proc_uid_seq_operations = {
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.start = uid_m_start,
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.stop = m_stop,
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.next = m_next,
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.show = uid_m_show,
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};
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struct seq_operations proc_gid_seq_operations = {
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.start = gid_m_start,
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.stop = m_stop,
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.next = m_next,
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.show = gid_m_show,
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};
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static DEFINE_MUTEX(id_map_mutex);
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static ssize_t map_write(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos,
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int cap_setid,
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struct uid_gid_map *map,
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struct uid_gid_map *parent_map)
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{
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struct seq_file *seq = file->private_data;
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struct user_namespace *ns = seq->private;
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struct uid_gid_map new_map;
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unsigned idx;
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struct uid_gid_extent *extent, *last = NULL;
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unsigned long page = 0;
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char *kbuf, *pos, *next_line;
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ssize_t ret = -EINVAL;
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/*
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* The id_map_mutex serializes all writes to any given map.
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*
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* Any map is only ever written once.
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*
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* An id map fits within 1 cache line on most architectures.
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*
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* On read nothing needs to be done unless you are on an
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* architecture with a crazy cache coherency model like alpha.
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*
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* There is a one time data dependency between reading the
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* count of the extents and the values of the extents. The
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* desired behavior is to see the values of the extents that
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* were written before the count of the extents.
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*
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* To achieve this smp_wmb() is used on guarantee the write
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* order and smp_read_barrier_depends() is guaranteed that we
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* don't have crazy architectures returning stale data.
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*
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*/
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mutex_lock(&id_map_mutex);
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ret = -EPERM;
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/* Only allow one successful write to the map */
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if (map->nr_extents != 0)
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goto out;
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/* Require the appropriate privilege CAP_SETUID or CAP_SETGID
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* over the user namespace in order to set the id mapping.
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*/
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if (!ns_capable(ns, cap_setid))
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goto out;
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/* Get a buffer */
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ret = -ENOMEM;
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page = __get_free_page(GFP_TEMPORARY);
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kbuf = (char *) page;
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if (!page)
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goto out;
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/* Only allow <= page size writes at the beginning of the file */
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ret = -EINVAL;
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if ((*ppos != 0) || (count >= PAGE_SIZE))
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goto out;
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/* Slurp in the user data */
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ret = -EFAULT;
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if (copy_from_user(kbuf, buf, count))
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goto out;
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kbuf[count] = '\0';
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/* Parse the user data */
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ret = -EINVAL;
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pos = kbuf;
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new_map.nr_extents = 0;
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for (;pos; pos = next_line) {
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extent = &new_map.extent[new_map.nr_extents];
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/* Find the end of line and ensure I don't look past it */
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next_line = strchr(pos, '\n');
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if (next_line) {
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*next_line = '\0';
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next_line++;
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if (*next_line == '\0')
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next_line = NULL;
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}
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pos = skip_spaces(pos);
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extent->first = simple_strtoul(pos, &pos, 10);
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if (!isspace(*pos))
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goto out;
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pos = skip_spaces(pos);
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extent->lower_first = simple_strtoul(pos, &pos, 10);
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if (!isspace(*pos))
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goto out;
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pos = skip_spaces(pos);
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extent->count = simple_strtoul(pos, &pos, 10);
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if (*pos && !isspace(*pos))
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goto out;
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/* Verify there is not trailing junk on the line */
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pos = skip_spaces(pos);
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if (*pos != '\0')
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goto out;
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/* Verify we have been given valid starting values */
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if ((extent->first == (u32) -1) ||
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(extent->lower_first == (u32) -1 ))
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goto out;
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/* Verify count is not zero and does not cause the extent to wrap */
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if ((extent->first + extent->count) <= extent->first)
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goto out;
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if ((extent->lower_first + extent->count) <= extent->lower_first)
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goto out;
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/* For now only accept extents that are strictly in order */
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if (last &&
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(((last->first + last->count) > extent->first) ||
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((last->lower_first + last->count) > extent->lower_first)))
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goto out;
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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;
|
|
}
|
|
|
|
/* 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)
|
|
{
|
|
user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
|
|
return 0;
|
|
}
|
|
module_init(user_namespaces_init);
|