1 files changed, 687 insertions, 163 deletions

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index d8c30db06c5b..03cb63883d04 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -1,18 +1,15 @@
-/*
- *  This program is free software; you can redistribute it and/or
- *  modify it under the terms of the GNU General Public License as
- *  published by the Free Software Foundation, version 2 of the
- *  License.
- */
+// 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/security.h>
 #include <linux/keyctl.h>
 #include <linux/key-type.h>
 #include <keys/user-type.h>
@@ -22,12 +19,27 @@
 #include <linux/ctype.h>
 #include <linux/projid.h>
 #include <linux/fs_struct.h>
+#include <linux/bsearch.h>
+#include <linux/sort.h>
+#include <linux/nstree.h>
 
-static struct kmem_cache *user_ns_cachep __read_mostly;
+static struct kmem_cache *user_ns_cachep __ro_after_init;
+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)
 {
@@ -38,6 +50,7 @@ static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
 	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);
@@ -47,6 +60,18 @@ static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
 	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
@@ -60,148 +85,327 @@ 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;
-	int ret;
+	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
+	 * 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())
-		return -EPERM;
+		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))
-		return -EPERM;
+		goto fail_dec;
+
+	ret = security_create_user_ns(new);
+	if (ret < 0)
+		goto fail_dec;
 
+	ret = -ENOMEM;
 	ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
 	if (!ns)
-		return -ENOMEM;
+		goto fail_dec;
 
-	ret = proc_alloc_inum(&ns->proc_inum);
-	if (ret) {
-		kmem_cache_free(user_ns_cachep, ns);
-		return ret;
-	}
+	ns->parent_could_setfcap = cap_raised(new->cap_effective, CAP_SETFCAP);
+
+	ret = ns_common_init(ns);
+	if (ret)
+		goto fail_free;
 
-	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;
+	}
+	set_userns_rlimit_max(ns, UCOUNT_RLIMIT_NPROC, enforced_nproc_rlimit());
+	set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
+	set_userns_rlimit_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING));
+	set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK));
+	ns->ucounts = ucounts;
 
-	set_cred_user_ns(new, ns);
+	/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
+	mutex_lock(&userns_state_mutex);
+	ns->flags = parent_ns->flags;
+	mutex_unlock(&userns_state_mutex);
 
-	update_mnt_policy(ns);
+#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);
+	ns_tree_add(ns);
 	return 0;
+fail_keyring:
+#ifdef CONFIG_PERSISTENT_KEYRINGS
+	key_put(ns->persistent_keyring_register);
+#endif
+	ns_common_free(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)
-		return -ENOMEM;
+	if (cred) {
+		err = create_user_ns(cred);
+		if (err)
+			put_cred(cred);
+		else
+			*new_cred = cred;
+	}
 
-	*new_cred = cred;
-	return create_user_ns(cred);
+	return err;
 }
 
-void free_user_ns(struct user_namespace *ns)
+static void free_user_ns(struct work_struct *work)
 {
-	struct user_namespace *parent;
+	struct user_namespace *parent, *ns =
+		container_of(work, struct user_namespace, work);
 
 	do {
+		struct ucounts *ucounts = ns->ucounts;
 		parent = ns->parent;
-		proc_free_inum(ns->proc_inum);
-		kmem_cache_free(user_ns_cachep, ns);
+		ns_tree_remove(ns);
+		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);
+		}
+#if IS_ENABLED(CONFIG_BINFMT_MISC)
+		kfree(ns->binfmt_misc);
+#endif
+		retire_userns_sysctls(ns);
+		key_free_user_ns(ns);
+		ns_common_free(ns);
+		/* Concurrent nstree traversal depends on a grace period. */
+		kfree_rcu(ns, ns.ns_rcu);
+		dec_user_namespaces(ucounts);
 		ns = parent;
-	} while (atomic_dec_and_test(&parent->count));
+	} while (ns_ref_put(parent));
 }
-EXPORT_SYMBOL(free_user_ns);
 
-static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
+void __put_user_ns(struct user_namespace *ns)
+{
+	schedule_work(&ns->work);
+}
+EXPORT_SYMBOL(__put_user_ns);
+
+/*
+ * struct idmap_key - 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;
+};
+
+/*
+ * 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)
 {
-	unsigned idx, extents;
+	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 */
-	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;
+			return &map->extent[idx];
 	}
-	/* Map the id or note failure */
-	if (idx < extents)
-		id = (id - first) + map->extent[idx].lower_first;
-	else
-		id = (u32) -1;
-
-	return id;
+	return NULL;
 }
 
-static u32 map_id_down(struct uid_gid_map *map, u32 id)
+static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
 {
-	unsigned idx, extents;
-	u32 first, last;
+	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);
 
-	/* 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;
+	if (extent)
+		id = (id - extent->first) + extent->lower_first;
 	else
 		id = (u32) -1;
 
 	return id;
 }
 
-static u32 map_id_up(struct uid_gid_map *map, u32 id)
+u32 map_id_down(struct uid_gid_map *map, u32 id)
 {
-	unsigned idx, extents;
-	u32 first, last;
+	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_range_up_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 */
-	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;
+		if (id >= first && id <= last &&
+		    (id2 >= first && id2 <= 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_range_up_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
+{
+	struct idmap_key key;
+
+	key.map_up = true;
+	key.count = count;
+	key.id = id;
+
+	return bsearch(&key, map->reverse, extents,
+		       sizeof(struct uid_gid_extent), cmp_map_id);
+}
+
+u32 map_id_range_up(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_up_base(extents, map, id, count);
+	else
+		extent = map_id_range_up_max(extents, map, id, count);
+
 	/* Map the id or note failure */
-	if (idx < extents)
-		id = (id - first) + map->extent[idx].first;
+	if (extent)
+		id = (id - extent->lower_first) + extent->first;
 	else
 		id = (u32) -1;
 
 	return id;
 }
 
+u32 map_id_up(struct uid_gid_map *map, u32 id)
+{
+	return map_id_range_up(map, id, 1);
+}
+
 /**
  *	make_kuid - Map a user-namespace uid pair into a kuid.
  *	@ns:  User namespace that the uid is in
@@ -212,7 +416,7 @@ static u32 map_id_up(struct uid_gid_map *map, u32 id)
  *
  *	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
+ *	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)
@@ -273,7 +477,7 @@ EXPORT_SYMBOL(from_kuid_munged);
 /**
  *	make_kgid - Map a user-namespace gid pair into a kgid.
  *	@ns:  User namespace that the gid is in
- *	@uid: group identifier
+ *	@gid: group identifier
  *
  *	Maps a user-namespace gid pair into a kernel internal kgid,
  *	and returns that kgid.
@@ -347,7 +551,7 @@ EXPORT_SYMBOL(from_kgid_munged);
  *
  *	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
+ *	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)
@@ -469,15 +673,20 @@ static int projid_m_show(struct seq_file *seq, void *v)
 	return 0;
 }
 
-static void *m_start(struct seq_file *seq, loff_t *ppos, struct uid_gid_map *map)
+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;
+	unsigned extents = map->nr_extents;
+	smp_rmb();
 
-	if (pos < map->nr_extents)
-		extent = &map->extent[pos];
+	if (pos >= extents)
+		return NULL;
 
-	return extent;
+	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)
@@ -512,28 +721,29 @@ static void m_stop(struct seq_file *seq, void *v)
 	return;
 }
 
-struct seq_operations proc_uid_seq_operations = {
+const 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 = {
+const struct seq_operations proc_gid_seq_operations = {
 	.start = gid_m_start,
 	.stop = m_stop,
 	.next = m_next,
 	.show = gid_m_show,
 };
 
-struct seq_operations proc_projid_seq_operations = {
+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)
+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;
@@ -548,7 +758,10 @@ static bool mappings_overlap(struct uid_gid_map *new_map, struct uid_gid_extent
 		u32 prev_upper_last, prev_lower_last;
 		struct uid_gid_extent *prev;
 
-		prev = &new_map->extent[idx];
+		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;
@@ -568,8 +781,154 @@ static bool mappings_overlap(struct uid_gid_map *new_map, struct uid_gid_extent
 	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_array(map->forward, map->nr_extents,
+				     sizeof(struct uid_gid_extent), GFP_KERNEL);
+	if (!map->reverse)
+		return -ENOMEM;
 
-static DEFINE_MUTEX(id_map_mutex);
+	/* 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,
@@ -578,16 +937,24 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 			 struct uid_gid_map *parent_map)
 {
 	struct seq_file *seq = file->private_data;
-	struct user_namespace *ns = seq->private;
+	struct user_namespace *map_ns = seq->private;
 	struct uid_gid_map new_map;
 	unsigned idx;
-	struct uid_gid_extent *extent = NULL;
-	unsigned long page = 0;
+	struct uid_gid_extent extent;
 	char *kbuf, *pos, *next_line;
-	ssize_t ret = -EINVAL;
+	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 id_map_mutex serializes all writes to any given map.
+	 * The userns_state_mutex serializes all writes to any given map.
 	 *
 	 * Any map is only ever written once.
 	 *
@@ -602,11 +969,12 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 	 * 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.
-	 *
+	 * order and smp_rmb() is guaranteed that we don't have crazy
+	 * architectures returning stale data.
 	 */
-	mutex_lock(&id_map_mutex);
+	mutex_lock(&userns_state_mutex);
+
+	memset(&new_map, 0, sizeof(struct uid_gid_map));
 
 	ret = -EPERM;
 	/* Only allow one successful write to the map */
@@ -616,33 +984,13 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 	/*
 	 * Adjusting namespace settings requires capabilities on the target.
 	 */
-	if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
-		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))
+	if (cap_valid(cap_setid) && !file_ns_capable(file, map_ns, CAP_SYS_ADMIN))
 		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];
+	for (; pos; pos = next_line) {
 
 		/* Find the end of line and ensure I don't look past it */
 		next_line = strchr(pos, '\n');
@@ -654,17 +1002,17 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 		}
 
 		pos = skip_spaces(pos);
-		extent->first = simple_strtoul(pos, &pos, 10);
+		extent.first = simple_strtoul(pos, &pos, 10);
 		if (!isspace(*pos))
 			goto out;
 
 		pos = skip_spaces(pos);
-		extent->lower_first = simple_strtoul(pos, &pos, 10);
+		extent.lower_first = simple_strtoul(pos, &pos, 10);
 		if (!isspace(*pos))
 			goto out;
 
 		pos = skip_spaces(pos);
-		extent->count = simple_strtoul(pos, &pos, 10);
+		extent.count = simple_strtoul(pos, &pos, 10);
 		if (*pos && !isspace(*pos))
 			goto out;
 
@@ -674,46 +1022,57 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 			goto out;
 
 		/* Verify we have been given valid starting values */
-		if ((extent->first == (u32) -1) ||
-		    (extent->lower_first == (u32) -1 ))
+		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)
+		/* 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)
+		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))
+		if (mappings_overlap(&new_map, &extent))
 			goto out;
 
-		new_map.nr_extents++;
-
-		/* Fail if the file contains too many extents */
-		if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
+		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 */
+	/* 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, ns, cap_setid, &new_map))
+	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;
-		extent = &new_map.extent[idx];
+
+		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,
-						extent->lower_first,
-						extent->count);
+						e->lower_first,
+						e->count);
 
 		/* Fail if we can not map the specified extent to
 		 * the kernel global id space.
@@ -721,25 +1080,46 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 		if (lower_first == (u32) -1)
 			goto out;
 
-		extent->lower_first = lower_first;
+		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 */
-	memcpy(map->extent, new_map.extent,
-		new_map.nr_extents*sizeof(new_map.extent[0]));
+	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:
-	mutex_unlock(&id_map_mutex);
-	if (page)
-		free_page(page);
+	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)
+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;
@@ -755,7 +1135,8 @@ ssize_t proc_uid_map_write(struct file *file, const char __user *buf, size_t siz
 			 &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)
+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;
@@ -771,7 +1152,8 @@ ssize_t proc_gid_map_write(struct file *file, const char __user *buf, size_t siz
 			 &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)
+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;
@@ -788,21 +1170,29 @@ ssize_t proc_projid_map_write(struct file *file, const char __user *buf, size_t
 			 &ns->projid_map, &ns->parent->projid_map);
 }
 
-static bool new_idmap_permitted(const struct file *file, 
+static bool new_idmap_permitted(const struct file *file,
 				struct user_namespace *ns, int cap_setid,
 				struct uid_gid_map *new_map)
 {
-	/* Allow mapping to your own filesystem ids */
-	if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1)) {
+	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, file->f_cred->fsuid))
+			if (uid_eq(uid, cred->euid))
 				return true;
-		}
-		else if (cap_setid == CAP_SETGID) {
+		} else if (cap_setid == CAP_SETGID) {
 			kgid_t gid = make_kgid(ns->parent, id);
-			if (gid_eq(gid, file->f_cred->fsgid))
+			if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
+			    gid_eq(gid, cred->egid))
 				return true;
 		}
 	}
@@ -813,7 +1203,7 @@ static bool new_idmap_permitted(const struct file *file,
 
 	/* 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.
+	 * 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))
@@ -822,7 +1212,120 @@ static bool new_idmap_permitted(const struct file *file,
 	return false;
 }
 
-static void *userns_get(struct task_struct *task)
+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 struct ns_common *userns_get(struct task_struct *task)
 {
 	struct user_namespace *user_ns;
 
@@ -830,17 +1333,17 @@ static void *userns_get(struct task_struct *task)
 	user_ns = get_user_ns(__task_cred(task)->user_ns);
 	rcu_read_unlock();
 
-	return user_ns;
+	return user_ns ? &user_ns->ns : NULL;
 }
 
-static void userns_put(void *ns)
+static void userns_put(struct ns_common *ns)
 {
-	put_user_ns(ns);
+	put_user_ns(to_user_ns(ns));
 }
 
-static int userns_install(struct nsproxy *nsproxy, void *ns)
+static int userns_install(struct nsset *nsset, struct ns_common *ns)
 {
-	struct user_namespace *user_ns = ns;
+	struct user_namespace *user_ns = to_user_ns(ns);
 	struct cred *cred;
 
 	/* Don't allow gaining capabilities by reentering
@@ -849,8 +1352,8 @@ static int userns_install(struct nsproxy *nsproxy, void *ns)
 	if (user_ns == current_user_ns())
 		return -EINVAL;
 
-	/* Threaded processes may not enter a different user namespace */
-	if (atomic_read(&current->mm->mm_users) > 1)
+	/* Tasks that share a thread group must share a user namespace */
+	if (!thread_group_empty(current))
 		return -EINVAL;
 
 	if (current->fs->users != 1)
@@ -859,34 +1362,55 @@ static int userns_install(struct nsproxy *nsproxy, void *ns)
 	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 		return -EPERM;
 
-	cred = prepare_creds();
+	cred = nsset_cred(nsset);
 	if (!cred)
-		return -ENOMEM;
+		return -EINVAL;
 
 	put_user_ns(cred->user_ns);
 	set_cred_user_ns(cred, get_user_ns(user_ns));
 
-	return commit_creds(cred);
+	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 unsigned int userns_inum(void *ns)
+static struct user_namespace *userns_owner(struct ns_common *ns)
 {
-	struct user_namespace *user_ns = ns;
-	return user_ns->proc_inum;
+	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,
-	.inum		= userns_inum,
+	.owner		= userns_owner,
+	.get_parent	= ns_get_owner,
 };
 
 static __init int user_namespaces_init(void)
 {
-	user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
+	user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC | SLAB_ACCOUNT);
+	ns_tree_add(&init_user_ns);
 	return 0;
 }
-module_init(user_namespaces_init);
+subsys_initcall(user_namespaces_init);