linux-stable/kernel/user_namespace.c
Christian Brauner f2a8d52e0a
nsproxy: add struct nsset
Add a simple struct nsset. It holds all necessary pieces to switch to a new
set of namespaces without leaving a task in a half-switched state which we
will make use of in the next patch. This patch switches the existing setns
logic over without causing a change in setns() behavior. This brings
setns() closer to how unshare() works(). The prepare_ns() function is
responsible to prepare all necessary information. This has two reasons.
First it minimizes dependencies between individual namespaces, i.e. all
install handler can expect that all fields are properly initialized
independent in what order they are called in. Second, this makes the code
easier to maintain and easier to follow if it needs to be changed.

The prepare_ns() helper will only be switched over to use a flags argument
in the next patch. Here it will still use nstype as a simple integer
argument which was argued would be clearer. I'm not particularly
opinionated about this if it really helps or not. The struct nsset itself
already contains the flags field since its name already indicates that it
can contain information required by different namespaces. None of this
should have functional consequences.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Jann Horn <jannh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
2020-05-09 13:57:12 +02:00

1325 lines
33 KiB
C

// 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;
}
/*
* 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 verifing 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;
ret = ns_alloc_inum(&ns->ns);
if (ret)
goto fail_free;
ns->ns.ops = &userns_operations;
atomic_set(&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 < UCOUNT_COUNTS; i++) {
ns->ucount_max[i] = INT_MAX;
}
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 (atomic_dec_and_test(&parent->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 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;
}
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;
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, 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 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(file, 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;
/* 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 had the approprpiate 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));
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);
return 0;
}
subsys_initcall(user_namespaces_init);